AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

The hemostatic system, consisting of blood vessels and blood, plays a crucial role in human survival. The importance of the plasma coagulation system in protecting life and preventing further blood loss following transection of a blood vessel has been understood for a long time. Blood normally is maintained in a fluid state, without evidence of bleeding or clotting. The presence of a bleeding diathesis in families with an X-linked pattern of inheritance of the disorder has been recognized for hundreds of years.

The recognition of factor deficiencies as the cause of hemophilias spurred investigations into the causes of other bleeding disorders and led to progress in understanding normal hemostasis. Knowledge of the fact that blood clots that are formed in the presence of calcium are stronger, insoluble in alkali, and resistant to proteolytic degradation led to the concept of insoluble clots in the earlier part of the last century. In 1948, Laki and Lorand recognized that a serum factor, termed fibrin stabilizing factor, was responsible for the characteristics of insoluble fibrin clots.¹ In 1960, Duckert et al described the first case of an "undescribed congenital haemorrhagic diathesis probably due to fibrin stabilizing factor deficiency," which was a description of the consequences of severe factor XIII (FXIII) deficiency.^{2, 3}

The importance of FXIII in the process of coagulation is underscored by symptoms borne by patients who are homozygously deficient in FXIII or who have an antibody that disrupts FXIII function. Paradoxically, alterations in FXIII may predispose patients to thrombosis. Based on all available data, FXIII is clearly involved in the clot preservation side of the delicate balance between clot formation and stability and clot degradation. FXIII participates in other physiologic processes, including wound repair and healing. The many functions of FXIII and the disruptions of those functions by mutations in the genes coding for FXIII are the subjects of on-going investigations.^{4, 5, 6}

Gene polymorphisms are being evaluated for their influence on susceptibility to venous and arterial thromboembolism. Variants of coagulation factors, including factor XIII Val34Leu, have been implicated in influencing susceptibility to thromboembolic diseases.⁷

There is a question as to whether factor XIII Val34Leu polymorphism is protective against idiopathic venous thromboembolism.⁸ The substitution of leucine for valine at amino acid position 34 of the factor XIII gene, commonly referred to as FXIII Val34Leu polymorphism, has been reported to confer protection against venous thromboembolism. However, the results of a recent study of white Canadian study population do not support an independent association of the FXIII Val34Leu polymorphism with idiopathic venous thromboembolism.

An association may exist between the factor XIII Leu allele and a modest protective effect against AMI and may provide useful information in profiling susceptibility to myocardial infarction.⁹

Pathophysiology

Structure, production, and half-life of FXIII

Plasma FXIII is a heterotetramer consisting of 2 identical proenzyme subunits (A₂) and 2 identical carrier protein subunits (B₂). Subunit A contains the catalytic site, the activation peptide, a calcium-binding site, and free sulfhydryl (SH) groups. Subunit B, a glycoprotein, acts as a carrier protein that stabilizes subunit A, binds the zymogen (subunit A) to fibrinogen, and acts as a brake on FXIII activation.^{10, 11} Subunit B circulates in plasma as part of the tetramer A₂B₂ and as a free B₂ dimer; all of plasma subunit A is complexed with subunit B. The concentration of subunit A in plasma is 15 mg/mL, while that of subunit B is 21 mg/mL. Much of FXIII circulates in blood in association with fibrinogen.^{12, 13}

Platelet FXIII (an A₂ homodimer) constitutes approximately 50% of total FXIII activity in blood. Plasma FXIII has a long half-life of approximately 9-14 days. A similarity exists between a portion of the carboxy terminal (C terminal) domain of FXIII and the receptor-binding region of a₂-macroglobulin. The complex of a₂-macroglobulin and its substrate protease is removed from the circulation by binding to its receptor in the liver and other tissues; therefore, as has been suggested, FXIII also may be removed from the circulation by a similar mechanism.¹⁴ Some features of the A and B chains of FXIII are listed below. Monoclonal antibodies and naturally occurring inhibitors are used to elucidate structure-activity relationships.

Bone marrow cells, megakaryocytes, and monocytes/macrophages synthesize FXIII, with a possible role for hepatocytes in the synthesis of subunit A. Subunit B is synthesized by the liver. Tissue transglutaminase, the intracellular form of FXIII, consists of the A₂ subunit (an A₂ homodimer) and is present in a variety of cells including platelets, megakaryocytes, monocytes/macrophages, and in the liver, placenta, uterus, prostate, and dermal dendrocytes.¹⁵ Red cells contain a transglutaminase that is activated by Ca²⁺ but is different from plasma transglutaminase in its cross-linking activity and can cross-link fibrinogen as well as fibrin. Trapped erythrocytes release FXIII when red cells lyse, providing additional cross-links to the aging thrombus.¹⁰

Some Features of the A and B Chains of Factor XIII

Comparative biology shows that transglutaminases are distributed widely in nature and may represent the prototype for the evolution of clotting enzymes.¹⁶ Partial homology of plasma FXIII exists with several proteins including tissue and keratinocyte transglutaminases, erythrocyte transglutaminase, and the hemocyte transglutaminase of the horseshoe crab and other zymogens of the same family.

A recent example is from the crystal structure of transglutaminase of the Red Sea bream, which shows that its active site and overall structure resemble that of human FXIII.¹⁷ These homologies attest to conservation of the enzyme during evolution. Since the gene structures are similar, it is believed that they evolved from a common ancestor. Subunit B contains 10 repeating "sushi" units linked by disulfide bonds; the function of the sushi unit is unknown. Sushi structures are present in at least 26 proteins, including proteins in the horseshoe crab and in the vaccinia virus.

Activation

Thrombin, generated by reactions initiated by activated tissue factor VII/factor IX pathways, leads to clot formation (see Image 1). Thrombin releases fibrinopeptide A from the a chain of fibrinogen, then fibrinopeptide B from the b chain of fibrinogen. Fibrin monomers (formed following the release of fibrinopeptides) polymerize spontaneously, which is followed by development of a complex branching clot as a result of the actions of activated FXIII (FXIIIa) (see Image 2).

Thrombin starts the process of FXIII activation by cleaving an activation peptide from subunit A. The subsequent Ca²⁺-dependent dissociation of subunit B allows FXIII activation to proceed. Calcium is important for activation of the zymogen (both FXIII and tissue transglutaminase require Ca²⁺), conformational changes, and opening of the catalytic site of FXIII to its substrate. Calcium also provides physical stability as determined by x-ray crystallography, computer modeling, and other studies; all of the changes allow the active subunit A to perform its functions optimally.^{10, 18, 19}

When activated by thrombin, tissue FXIII functions in the same manner as plasma FXIIIa. Platelet FXIII undergoes nonproteolytic activation following the platelet activation-induced rise in cytosolic Ca²⁺. Activation of the red cell enzyme occurs upon exposure to Ca²⁺, and red cells that are present in the fibrin clot lyse and release their FXIII as the clot ages. Several controls in the complex activation process focus the actions of FXIIIa on fibrin rather than on fibrinogen, and cross-linking of polymerized soluble fibrin by FXIIIa is the final step in hemostasis. For extensive details of this activation process, the reader is referred to two recent reviews by Lorand^{16, 10} (see Image 3).

Role of FXIII in cross-linking and resistance to lysis

FXIIIa cross-links the lysine of one g chain in the fibrin polymer with the glutamine of another g chain by transamidation, releasing ammonia in the process. Additional cross-links occur between a-a chains, a-g chains, a chains-a₂-plasmin inhibitor (a₂PI), and a chains-fibronectin. As a result of the extensive cross-linking actions of FXIIIa, the clot structure of fibrin polymers increases in complexity from dimers to trimers to tetramers.

The g chains of fibrinogen and fibrin normally bind to the platelet membrane glycoprotein IIb/IIIa complex. The same g chains are subject to cross-linking by FXIIIa; therefore, cross-linking also occurs between fibrin and the platelet membrane. Both plasma FXIIIa and platelet FXIIIa cross-link fibrin polymers, but under physiologic conditions, platelet FXIII is believed to play a minor role.²⁰ Red cell FXIII is responsible for hybrid cross-linking of a-g chains, in contrast to the actions of plasma FXIII.

Dysfibrinogenemias and dyshypofibrinogenemias result in alterations in fibrin (substrate for FXIIIa), which can interfere with the ability of FXIII to cross-link fibrin. A reduction in available fibrin resulting from afibrinogenemia can have the same effect. Conversely, increased fibrinogen levels have been identified as a risk factor for thrombosis.

Mechanisms of this risk were elucidated by a fibrinolysis assay containing purified components. The assay showed that lysis of fibrin decreased as fibrinogen levels increased, and the presence of a minor common variant of fibrin (g') is associated with accelerated cross-linking, which made the clot resistant to proteolysis by both plasmin and trypsin. Increased clot stability also was believed to result from increased concentration of FXIII in the clot. Non-cross-linked fibrin potentiates activation of FXIII by thrombin; thus, the substrate potentiates its enzyme, further contributing to clot stability.^{13, 21, 22}

Cross-linking of a₂PI to a chains of fibrin by FXIIIa brings the principal inhibitor of plasmin to the site of the clot, ensuring resistance of the clot to proteolysis. Inhibition of a₂PI in in vitro systems leads to enhanced clot lysis. In humans, deficiency of a₂PI results in a bleeding disorder because of vulnerability of the fibrin clot to prompt degradation by plasmin. The formation of highly cross-linked a-fibrin polymers in the presence of high concentrations of FXIIIa produces clots that are highly resistant to fibrinolysis.

Fibronectin, an adhesive protein, is a large component (approximately 4%) of the proteins in a fibrin clot, is present in plasma and cells, and is subject to cross-linking by both plasma and cellular FXIII. Cross-linking of fibronectin to fibronectin and fibronectin to fibrin is accomplished by FXIIIa, with fibronectin contributing to increased fiber size, density, and strength of the clot. FXIIIa also cross-links actin to fibrin and actin to myosin. Cross-linking of intracellular structural proteins is involved in clot retraction and cell migration. This complex gel network created by the actions of FXIII plays an important role in wound healing, cell adhesion, and cell migration. All of these cross-linking reactions impart increased mechanical strength to the clot, contributing to clot retraction and resistance of the clot to degradation by plasmin and providing an explanation for the known plasmin resistance of older clots.

Many other proteins function as substrates for FXIIIa, including von Willebrand factor (vWF), factor V (FV), thrombospondin, gelsolin, vitronectin, vinculin, lipoprotein (a), and collagen (FXIIIa cross-links collagen with fibronectin and vWF, attaches the clot to the vessel wall, impacts tissue repair, increases resistance of collagen to proteolysis, and modulates synthesis of collagen by fibroblasts). Thus, FXIII plays a role in a wide array of cross-linking reactions involving plasma proteins at the intracellular level, impacting many different functions.

Factors affecting level and activity of FXIII

When quantitative amine incorporation assays became available, healthy people were found to have an 8-fold spread in FXIIIa activity.²³ In recent studies of FXIII antigen and activity in humans, no correlation was found between these two parameters. During the search for an explanation, 23 unique FXIIIa genotypes were found. The Leu34 and Leu564 variants gave rise to increased specific activity; the Phe204 variant lowered specific activity. Other mutations gave rise to low, high, or median FXIII-specific activity, and some variants had no effect.^{24, 25}

In a study of the variability of FXIII levels in racial groups, FXIII activity was found to be higher in Asian Indians (male and female) than in their Chinese counterparts, accounting for approximately one fourth of the variability. Common genetic polymorphisms in the A and B chains appeared to contribute to the differences.²⁶ An influence exerted by acquired factors was evident in the higher FXIII levels found in women who smoked 20 or more cigarettes per day during a normal pregnancy than was found in nonsmokers, with a lesser drop in the second half of pregnancy.²⁷

Role of FXIII in pregnancy

In the latter half of pregnancy, some drop in FXIII levels is normal, but severe (homozygous) FXIII deficiency is a cause of recurrent miscarriages. In a study of gestational tissues, FXIII was found in the decidual layer of the placenta, while FXIII secretion was evident in cultures of round-shaped endometrial cells. A study of early (7-8 wk) gestational tissues obtained from women without FXIII deficiency and from a woman who was homozygous for FXIII deficiency showed poorly formed cytotrophoblastic shells and Nitabuch layers, along with absence of FXIIIa in tissues obtained from the woman with FXIII deficiency. Low plasma levels of FXIII appear to correlate with low placental levels of FXIII with poor trophoblastic development, which may be the cause of spontaneous miscarriages.

It has been suggested that preventing miscarriage in patients who are severely deficient requires FXIII supplementation beginning at approximately 5 weeks of gestation because FXIII, fibrinogen, and fibronectin are necessary to anchor cytotrophoblasts invading the endometrium.^{28, 29} Reduced FXIII activity resulting from the Tyr204Phe mutation has been associated with repeated miscarriages.³⁰

Role of FXIII in wound healing

Physiologically, hyperpermeability induced by severe metabolic inhibition of porcine aortic endothelial cells is prevented by FXIIIa, which is similar to the maintenance of endothelial barrier function by FXIIIa despite depletion of energy or during reperfusion of ischemic rat hearts.³¹ In a different system, FXIII induced epithelial wound healing by increasing cell growth by approximately 2.5 fold, leading to replacement of damaged cells.³² Smooth muscle cell migration, an integral part of the healing process, is facilitated by FXIII. Migration of smooth muscle cells in cross-linked fibrin gels was twice the migration seen in non–cross-linked gels, demonstrating the importance of the 3-dimensional clot structure created by cross-linking in smooth muscle cell migration.³³ In humans, Fibrogammin was shown to contribute to the healing of venous leg ulcers by reducing endothelial permeability.³⁴

Effects of other agents on FXIII

Nitric oxide (NO), an important diffusible molecular messenger, is increasingly recognized as having an impact on coagulation proteins. Activity of plasma transglutaminase is inhibited by NO via nitrosylation of critical thiol groups (reactive cysteine residue), resulting in inhibition of both g-chain cross-linking and insoluble clot formation. NO donors and carriers inhibit FXIII activity in a dose-dependent manner, in a purified system and in plasma. Tissue transglutaminases are involved in apoptosis, and inhibition of their activity by NO prevents apoptosis.^{35, 36}

Venoms and toxins can affect clot stability. Excessive bleeding resulting from envenomation can affect the functions of FXIII in different ways. Acuthrombin A, one of two proteases in the venom of Agkistrodon acutus (five-pace snake), activates FXIII.³⁷ Ancrod, obtained from the venom of Agkistrodon species, causes defibrination, thereby removing the substrate for FXIII.

A severe systemic bleeding disorder may develop several hours after initial contact with 2 types of caterpillars in the Saturniidae family (from Brazil and Venezuela). Intracranial and intracerebral bleeding and renal failure may follow. In this case, FXIII reduction results from generalized disseminated intravascular coagulation (DIC) induced by several activities directed against the hemostatic mechanism, including a FXIII proteolytic-urokinase–like activity.³⁸ Tridegin, a peptide inhibitor of FXIII present in the saliva of an Amazon leech (Haementeria ghilianii) accelerates fibrinolysis by inhibiting FXIIIa; tridegin is under investigation as a potential new antithrombotic agent. Destabilase, an enzyme present in the leech, hydrolyzes g-g fibrin cross-links and breaks down blood clots.³⁹

Simvastatin is a commonly used cholesterol-lowering agent. A non–antibody-mediated drug-induced reduction in FXIII activity as part of a broader reduction in hemostatic activation has been suggested to be the reason for the proven antithrombotic efficacy of simvastatin in clinical trials.⁴⁰ Blood samples were obtained sequentially every 30 seconds from a bleeding time cut in patients with coronary artery disease, before and 3 months after simvastatin treatment. Samples were analyzed for the time-course drop in fibrinogen levels and activation of factors II, V, and XIII by quantitative Western blot analyses. Simvastatin, independent of its effects on cholesterol, significantly reduced the rate of blood clotting, as evidenced by reduced formation of several activation products including FXIIIa.

Several selective synthetic inhibitors have been shown to prevent the ability of FXIIIa to stabilize a clot, thereby reducing clot strength (clot stiffness, viscoelastic modulus) to approximately 20% of normal (values similar to those seen in patients with severe FXIII deficiency). Rapid lysis of these clots occurred following in vitro exposure to thrombolytic agents.¹⁶ Imidazolium derivatives, a new class of compounds, specifically inhibit both FXIII-induced formation of a-chain polymers and the incorporation of a₂PI into the a chain of fibrin, resulting in accelerated clot lysis.^{41, 6}

Specific monoclonal antibodies to FXIII have provided similar benefits by reducing the viscoelastic properties and by enhancing clot lysis. They also have been used to modify disease states. The beneficial effect of the absence of cross-linked fibrin on pathophysiologic processes was proven in an animal model of widespread thrombosis. FXIIIa deficiency induced in rabbits by pretreatment with a specific monoclonal antibody before induction of a generalized Schwartzman reaction protected them from the deleterious effects of widespread microvascular thrombosis. The protection resulted from the ability of the fibrinolytic system to effectively degrade non–cross-linked thrombi.⁴² These data add support to the author's speculation many years ago of the potential use of drugs that inhibit cross-linking as a method of prophylaxis in venous thromboembolic disease.

The biochemical basis and potential for using modifiers of fibrin stabilization in improved thrombolytic therapies are discussed in a recent review by Lorand.¹⁶ Similar ideas have been proposed by others, expanding on the importance of fibrin structure in thrombus formation and dissolution.⁴³ Prospective clinical trials must prove any thromboprophylactic efficacy of altering fibrin structure using specific drugs.

Other functions of FXIII

Plasma and tissue transglutaminases have been reported to promote cell adhesion through specific integrins for 2 different tumor cell types, MOLT-3 human lymphocyte–like leukemia and melanoma cells and SW480 colon cancer cells transfected with a ligand.⁴⁴ In contrast, FXIII did not stimulate growth of cultured human tumor cells.⁴⁵ An intriguing observation is the potential use of subunit A of FXIII and FXIII activity as a tumor marker in malignant brain tumors; its presence may distinguish benign from malignant brain tumors.⁴⁶ Recently, it was shown for the first time that intranuclear accumulation and cross-linking activity of FXIIIa occurred in maturing monocytes, supporting the hypothesis that FXIIIa may be involved in cell proliferation/differentiation, chromatin structure remodeling, and even cell death.⁴⁷ Further data are needed to unravel the role of FXIII in malignancies.

An unexpected role has been postulated for FXIII in degenerative brain disorders. In Alzheimer disease and spongiform encephalopathies, the brain contains fibrils that develop from native proteins containing a discordant a helix. Human FXIII was found to form fibrils in buffered saline, suggesting that FXIII, in addition to several other proteins, can be a source of this abnormal fibrillar protein.⁴⁸

Possible interactions between deficiencies of FXIII and thrombin-activatable fibrinolytic inhibitor

Thrombin-activatable fibrinolytic inhibitor (TAFI), a single-chain carboxypeptidase B–like zymogen, is activated by thrombin to become activated TAFI (TAFIa).⁴⁹ The importance of TAFIa in fibrinolysis is emphasized by the fact that the conversion of only 1% of the zymogen to TAFIa is sufficient to suppress fibrinolysis by approximately 60%.

TAFIa suppresses fibrinolysis by removing C-terminal lysine and arginine residues exposed in the partially degraded fibrin clot produced by plasmin. Removal of C-terminal lysine residues from fibrin reduces the rate of plasminogen activation by a number of mechanisms, attenuating fibrinolysis. This effect is counterbalanced in normal plasma by activation of protein C, which has profibrinolytic properties because of its ability to suppress thrombin generation via its major effect of degrading activated factor V (FVa), and to a lesser extent, activated factor VIII (FVIIIa).^{49, 50, 51}

A delicate balance usually exists between thrombus formation and thrombus resolution; thrombin secures survival of the thrombus created by its action on fibrinogen by activating TAFI, thereby inhibiting fibrinolysis. Cross-linking of fibrin induced by FXIIIa (activated by thrombin) renders the clot insoluble. FXIII deficiency results in absence of cross-linked fibrin leading to premature lysis of the clot by the fibrinolytic system, with adverse consequences including bleeding. Theoretically, a deficiency of TAFI leading to decreased suppression of fibrinolysis (enhanced clot lysis) can potentiate bleeding resulting from FXIII deficiency (also associated with enhanced clot lysis) (see Image 4).

Cell surface–directed hemostasis

The concept of coagulation as a waterfall or cascade effect has been acknowledged for a long time, with platelets and other cell surfaces providing the anionic phospholipids needed for complex formation so that reactions can proceed efficiently. A recent review proposes that coagulation is essentially a cell surface–based event.⁵² Platelet FXIII is positioned appropriately to influence the process (see Image 5).

Conclusion

Much work is needed, even in the clinical arena, to clarify the relationship between the exact levels of FXIII and hemorrhagic or thrombotic phenotypes. Establishing an international registry of patients deficient in FXIII would be of value in improving understanding of the protean manifestations of this uncommon disorder.

Frequency

United States

Overall estimated frequency of the autosomal recessive disorder involving a severe deficiency of subunit A is approximately 1 case per 2 million population. Previously, consanguinity was believed to be necessary, but the detection of compound heterozygotes by the application of molecular techniques is changing that perception. Approximately 200 cases of FXIII deficiency have been described thus far.⁵³ See Other Problems to be Considered for a discussion of acquired FXIII deficiency related to diseases or inhibitors.

International

• FXIII deficiency has been reported in many ethnic groups around the world, including persons from Canada, Europe, India, Israel, Japan, Kuala Lumpur, Pakistan, Papua New Guinea, South America, Thailand, Turkey, and the United States.
• Diagnosis of disorders of FXIII inhibitors, which may have been missed in the past, is increasing as more laboratory support becomes available around the world. An increasing use of isoniazid (INH) to combat a worldwide rise in incidence of tuberculosis could contribute to an increased incidence of FXIII inhibitors in patients.
• Variability in the distribution of mutations is exemplified by existing data, ie, significant ethnic heterogeneity was found in a Brazilian population in which the Val34Leu mutation was present in 51.2% of American Indians, 44% of whites, 28.9% of Africans, and in only 2.5% of Japanese Asians.⁵⁴

Mortality/Morbidity

Umbilical bleeding starting in the first few days after birth, recurrent intracranial bleeding, and recurrent early miscarriages are hallmarks of FXIII deficiency.

• Approximately 30% of central nervous system (CNS) bleeding is recurrent, and approximately 50% of CNS bleeding may be fatal, but the severity of bleeding varies from family to family. Posttraumatic bleeding may be immediate, delayed, or recurrent. Traumatic joint bleeding may develop. Poor wound healing has been described, although this is not a universal finding.
• Cryoprecipitate and fresh frozen plasma (FFP) provide a source of FXIII for most patients. All plasma-derived products carry risks of transmitting hepatitis, HIV, parvovirus B19, transfusion transmitted virus (TTV), and prion-induced (new variant Creutzfeldt-Jacob disease [nvCJD]) illnesses (see Complications and eMedicine article Factor VIII for more information). Plasma-derived FXIII concentrates are being tested at centers. Recombinant factor XIII (rFXIII) subunit A concentrates are yet to be tested widely.
• Development of FXIII inhibitors (alloantibodies or autoantibodies) is associated with significant morbidity and mortality.

Race

No predilection exists for FXIII deficiency. FXIII deficiency has been reported widely. The restriction of certain polymorphisms to specific populations should be expected.

Sex

Since it is an autosomal disorder, homozygous FXIII deficiency occurs in either sex. Acquired inhibitors to FXIII can present in either males or females.

Age

• Physiologically, reduced levels of FXIII are found in healthy newborns, with a gradual rise in levels into the reference range. Premature infants have lower values than full-term neonates. FXIII levels drop in the latter half of a normal pregnancy.
• Severe FXIII deficiency may present with bleeding from the umbilical cord after birth. Easy bruising and delayed and recurrent bleeding after trauma begin in childhood. Oral bleeding can begin with teething and cuts or abrasions to the lips, tongue, and frenulum. Bleeding remains a problem throughout life and requires replacement therapy. FXIII deficiency acquired as a result of autoantibodies has been reported in the older population, as has acquired hemophilia A. Both drug-induced autoantibodies and alloantibodies have been reported in patients who are severely deficient and receiving replacement therapy.

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

History

The following symptoms should trigger an evaluation for FXIII deficiency:

• Spontaneous miscarriages occur early in pregnancy.
• Bleeding from the umbilical cord has been reported to develop from 1-19 days after birth.
• Easy bruising and soft tissue bleeding, particularly in association with trauma, occur as the infant starts to ambulate. Bleeding following trauma may be immediate, delayed, and/or recurrent.
• CNS hemorrhage is common, recurs in approximately 30% of patients, and may be the initial manifestation in patients with severe FXIII deficiency.
• CNS bleeding may be preceded by head trauma in children, while adults may develop a CNS bleed in the absence of obvious trauma.
• Symptoms typical of any CNS event may be present, eg, headaches, seizures, vomiting, and focal neurologic defects. Symptoms may be acute at onset or may be superimposed on residual findings of a past bleed.
• Menorrhagia and intra-abdominal bleeding during menses may be present.
• Bleeding into joints may be precipitated by trauma. Although reports exist of recurrent target joint bleeds, destructive changes in the joints are uncommon.⁵⁵ Spontaneous joint and extensive muscle bleeding, characteristic of patients with severe hemophilia, are uncommon in patients with severe FXIII deficiency.
• The severity of bleeding is variable. An unusual example is the history of a very mild bleeding disorder in 2 sisters despite severely reduced levels of FXIII (<1%). One of the sisters had 2 successful pregnancies without product replacement (see Causes for details).⁵⁶
• Poor wound healing, although described, is less common.
• Heterozygous parents of a propositus with severe bleeding usually are asymptomatic, although some cases of bleeding in heterozygotes have been reported.
• Development of alloantibodies is a serious complication that results in increased bleeding and a lack of response to usual therapy. This condition can be fatal (see Other Problems to be Considered for more information).
• Autoantibodies to FXIII are an acquired cause of a bleeding diathesis. A detailed drug history is essential in assessing the possible contribution to inhibitor development. As the frequency of tuberculosis rises worldwide and the use of INH increases, the number of patients with inhibitors may increase (see Other Problems to be Considered for more information).
• Patients may have acute and/or chronic viral illnesses transmitted by less pure products, such as FFP or cryoprecipitate, that are used to treat bleeding. HIV-related illnesses, AIDS, chronic hepatitis, progressive hepatic failure, and parvovirus-related illnesses present in the usual manner.

Physical

Physical findings depend on the site at which bleeding develops and include the following:

• Bleeding from the umbilical cord after birth usually manifests with persistent oozing, which may start a few days after birth.
• Findings associated with CNS bleeding depend on the location of the bleeding. Trauma may precede the event, with additional findings. A new CNS bleed may be superimposed on residual findings related to a prior bleed.
• Findings in patients with bruising and soft tissue bleeding are similar to those seen in other patients; it is uncommon to find the large hematomas or joint bleeds characteristic in patients with severe hemophilia.
• Patients may present with vaginal spotting or bleeding during early pregnancy, preceding a spontaneous miscarriage.
• Persistent, delayed, or recurrent bleeding may occur at sites of trauma or surgery.
• Poor wound healing may be noted.
• Acquired causes of FXIII deficiency, such as DIC and liver disease, present in a well-recognized manner.

Causes

• To date, most identified mutations leading to severe FXIII deficiency and a bleeding disorder involve subunit A, with very few mutations reported involving subunit B. The gene for subunit A is located on chromosome 6 bands p24-25. The gene is 160 kilobases in length and has 15 exons and 14 introns with specific structural and functional domains. Catalytic activity is encoded in the second exon, and the active cysteine is encoded by the seventh exon. The 2 Ca²⁺-binding sites and a thrombin-inactivation site have been identified at other locations (see Image 6). The gene for subunit B is located on chromosome 1 bands q31-32.1, is 28 kilobases in length, and has 12 exons and 11 introns.^{5, 57}
• Detailed characteristics of complementary ribonucleic acid (cRNA) and messenger ribonucleic acid (mRNA) of the placental subunit A are known. The presence of an acetylated amino terminal end and the absence of glycosylation and disulfide bonds apparently are features typical of secreted cytoplasmic proteins. The presence of these characteristics makes it conducive for subunit A expressed in yeast systems to make a recombinant product.
• Substitutions in the core domain of the enzyme, affecting highly conserved residues, result in a serious defect in structure and function. Missense mutations in the A chain are a common cause, accounting for approximately 50% of cases of severe FXIII deficiency. The defects result in an absence of subunit A protein but also are accompanied by a reduction in subunit B carrier protein (type II defect).
• Nonsense mutations are an equally common cause of A chain defects, resulting in a frameshift-type, splice-type, or termination-type mutation. The few defects that have been reported in the B chain lead to a deficiency of the carrier protein (subunit B), which then leads to instability and reduction of plasma subunit A levels despite the presence of functional intracellular subunit A (type I defect).⁵⁸ Therefore, patients who are homozygous for subunit B mutations have a bleeding disorder. Most recently, impaired intracellular transport from the endoplasmic reticulum to the Golgi apparatus, with failure of secretion of the truncated FXIII subunit B produced by a single-base deletion, was reported to be the cause of severe FXIII deficiency in 3 unrelated patients.⁵⁹
• Many kinds of mutations have been (and continue to be) identified, with some mutations unique to certain families. The finding of compound heterozygotes has eliminated the mandatory search for consanguinity in all parents of patients with severe FXIII deficiency.^{60, 61, 30}
• An unusual mutation has been described in 2 Finnish sisters with a very mild bleeding disorder.
• • One sister had 2 successful pregnancies without regular replacement therapy.
  • The sisters had no detectable subunit A activity (<1%) using plasma screening tests; however, using the 3H-putrescine incorporation assay, subunit A showed 0.35% of normal activity, with partial g-g dimerization of fibrin in clotted plasma.
  • A full-length subunit A was detected in the patients' platelets using Western blot analysis.
  • The sisters had an Arg661-->stop mutation on one allele and a T-->C transition on the other allele. These data showed that a mutation in the splice donor site of intron C can result in different variant mRNA transcripts and that small amounts of correctly processed mRNA can produce a type of FXIII that can produce, at least, dimerization of fibrin, thus minimizing the clinical consequences.⁵⁶
• Various reported mutations are spread throughout the gene coding for FXIII without specific hot spots. In many patients, low steady-state mRNA levels have been found, which result in inefficient production of the abnormal protein.⁶
• Data in the literature conflict regarding the impact of the common FXIII subunit A Val34Leu mutation (associated with higher plasma transglutaminase activity) on thrombotic disease.
• • The Val34Leu mutation continues to be studied in different populations because current data provide conflicting evidence about its causal role in coronary artery disease. The Val34Leu mutation appears to protect whites but not Asian Indians from myocardial infarction. However, in the Asian Indian population in Britain, a strong link was found between FXIII subunit B levels and risk factors for cardiovascular disease and, possibly, insulin resistance.⁶²
  • In separate studies, a higher frequency of the Val34Leu mutation was found in whites with primary intracerebral hemorrhage; however, the mutation reportedly was associated with a reduction in brain infarcts.
• A possible cooperative interaction between the Val34Leu mutation and other known thrombophilic mutations also has been explored.
• • In a study of patients from southern France, a higher than usual odds ratio was found for the association between carriers of an angiotensin receptor mutation and coronary artery disease, but no association was found between the disease and any of the FXIII polymorphisms that were studied.⁶³
  • A study of the contribution of the Val34Leu mutation to thrombotic risk in a large number of carriers of factor V Leiden (who were relatives of thrombotic propositi with factor V Leiden) found a very modest contribution of the Val34Leu mutation to venous thrombotic disease.⁶⁴
  • This study contrasts with a report of a protective role of the mutation in venous thrombosis.⁶⁵
  • A recent review discusses the possible role of FXIII in vascular diseases.⁶⁶ The FXIII Val34Leu mutation does not appear to influence the induction or modification of the course of inflammatory bowel disease.
• Genetic polymorphisms affecting both the A and B subunits have been reported, but because they do not involve conserved amino acids or are not important for protein structure, they do not result in FXIII deficiency and bleeding. Based on an analysis of polymorphisms in the gene for FXIII subunit A and their products in a northern Portuguese population, it has been stated that the evolutionary order of appearance of the main protein alleles for FXIII is 1B-->2B-->1A-->2A and that intragenic combinations are likely to have played a role in the molecular diversity in the main FXIII subunit A alleles.⁶⁷
• Genetic polymorphisms and, particularly, intragenic polymorphisms are useful in genetic counseling of families with unknown mutations. For example, 80% of whites are heterozygous for a tetrameric repeat in intron 1 of subunit A, which can help differentiate defects in subunit A from defects in subunit B.^{5, 6, 57, 68} Some polymorphisms are universal, while others appear to be restricted to particular ethnic groups. The latter situation will change as ethnic intermarriages increase in this global society. Families with severe FXIII deficiency associated with a serious disabling bleeding disorder have access to all of the genetic tools available to patients with hemophilia A and B.
• Disorders of fibrin stabilization can affect the activity of FXIII or its substrates fibrin and fibrinogen. A proposed classification of disorders leading to a positive urea solubility test result is presented below.

  Disorders of Fibrin Stabilization (Positive Urea Solubility Test)

  ---

  1. Abnormalities of FXIII (enzyme)
  2. 1. Genetic mutations
     2. • Subunit A
        • Subunit B
        • Subunits A and B
     3. Acquired
     4. • Decreased production, ie, liver disease
        • Increased loss due to excessive activation, ie, DIC, exposure to snake venoms and caterpillar toxins
        • Secondary to inhibitors, ie, alloantibodies and autoantibodies
  3. Abnormalities of the substrate for FXIII (fibrin/fibrinogen)
  4. 1. Genetic
     2. • Afibrinogenemia
        • Dyshypofibrinogenemia
     3. Acquired
     4. • Decreased production, ie, acute massive hepatic necrosis or severe chronic liver disease
        • Increased loss resulting from defibrination syndromes, ie, DIC, exposure to snake venoms and caterpillar toxins, and systemic hyperfibrinolysis (drug induced or disease induced)

  ---

• Although gene therapy has not been used as a treatment modality in patients with FXIII deficiency thus far, the reader is referred to a review of gene therapy in the hemophilias⁶⁹ and a review on the use of gene therapy in malignancy, which provides an excellent overview of the advantages and disadvantages of various approaches to gene therapy.⁷⁰

DIFFERENTIALS

Section 4 of 11  

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Other Problems to be Considered

FXIII alloantibodies (which can be a cause of bleeding in patients with inherited severe FXIII deficiency who receive FXIII replacement)

Rare inherited afibrinogenemia or dyshypofibrinogenemias associated with a bleeding disorder

a₂-Plasmin inhibitor deficiency

Plasminogen activator inhibitor-1 deficiency

Hemophilia A or B (should be excluded, particularly in a male with delayed onset, recurrent bleeding after trauma or surgery, or with a joint bleed)

Bleeding in a patient with type III von Willebrand disease (may mimic hemophilic bleeding)

Inherited severe bleeding disorders affecting platelet function, eg, Glanzmann thrombasthenia

All other rare coagulation factor deficiencies (FII, FV, FVII, FX); all of these factor deficiencies are associated with abnormalities in routine screening coagulation tests (eg, activated partial thromboplastin time [aPTT], prothrombin time [PT]).

Acquired disorders

FXIII deficiency should be considered in patients with recurrent miscarriages and recurrent intracranial bleeding.

Any cause of DIC can lead to an acquired reduction in fibrinogen and FXIII.

Liver disease may result in decreased production of FXIII and fibrinogen (also can produce dysfibrinogenemia).

Cardiopulmonary bypass: Activation of hemostasis is an integral part of any cardiopulmonary bypass procedure. FXIII antigen levels and clot strength as measured by thromboelastography (TEG) were reduced in parallel with platelet count and fibrinogen levels after bypass; changes were secondary to increased thrombin generation.⁷¹

Malarial infections: Malaria affects a sizable population worldwide. Patients who are severely ill with falciparum malaria have activity levels of subunit A lower than 50%, with an increase during antiparasitic therapy. An inverse relationship has been found between FXIII levels, clinical severity of the disease, degree of parasitemia, and human neutrophil elastase levels.⁷²

A significant reduction in FXIII subunit A levels has been found in patients with active Crohn disease, ulcerative colitis, and infectious colitis, without any change in the levels of the carrier protein (subunit B). A reduction in FXIII activity was associated with a concomitant increase in fibrinogen/fibrin split products correlating with inflammatory bowel disease activity during a yearlong follow-up study of patients with severe ulcerative colitis. The predictive value of such changes is yet to be confirmed in prospective clinical trials.

Reduced levels of FXIII have been reported in patients with scleroderma and Henoch-Schönlein purpura and in advanced malignancies.

Following systemic thrombolytic therapy, severe reduction in the fibrinogen level (hypofibrinogenemia) also is associated with a dysfibrinogenemia. A specimen obtained from a patient who has systemic fibrinolytic effects may show a false-positive urea solubility test result because of an acquired abnormality in the substrate for FXIII (dyshypofibrinogenemia).

FXIII inhibitors

A wide variety of bleeding manifestations, which are not necessarily specific for an FXIII inhibitor, occur in patients with antibodies that inhibit FXIII function. Manifestations include persistent serious bleeding after trauma or surgery (including dental extractions); large hematomas over the extremities and abdominal wall; intramuscular, retroperitoneal, and intra-abdominal bleeding; gastrointestinal (GI) tract, urinary tract, and CNS bleeding; menorrhagia; prolonged postpartum hemorrhage; and spontaneous miscarriage.

Very few FXIII inhibitors have been reported thus far; they usually include immunoglobulin (Ig) G classes and may be monoclonal or polyclonal. Alloantibodies may arise in patients with deficiency who receive factor replacement or in patients who have received transfusions with blood products. Incidence of alloantibodies in patients with inherited FXIII deficiency appears to be approximately 1%, but a larger database is needed before the frequency is established with certainty.

Autoantibodies may be idiopathic, secondary to drugs or autoimmune diseases. Many reported FXIII antibodies were believed to be secondary to long-term ingestion of certain drugs. The most commonly implicated drug is INH, which functions as a lysine analog and acts as a false substrate for FXIII. Other drugs that have been reported to induce antibodies include penicillin (allergy), procainamide, and phenytoin sodium.

Antibodies to FXIII may inhibit any of several functions, including activation of FXIII to FXIIIa and transamidating function of FXIIIa. Antibodies may bind to fibrin, preventing it from binding to FXIIIa, or antibodies may bind to the fibrin-binding site on FXIIIa, thus blocking its ability to bind to fibrin. Antibodies may inhibit other functions, such occurs at the a₂PI cross-linking site.^{73, 6, 74} Both plasma and platelet zymogens and their active enzymes may be the target of the antibody. All studied inhibitors neutralize plasma cross-linking activity of FXIII, and most also inhibit in vitro amine incorporation tests. Many inhibitors specific for subunit A also are associated with a reduction in the antigenic amount of subunit B, although the inhibitor is not directed against subunit B. Currently, the reasons for this are not clear.

Patients with acquired FXIII inhibitors usually are older and present with a new onset of a bleeding disorder, similar to the mode of presentation of patients with acquired factor VIII (FVIII) inhibitors. The mortality rate is high, and to date, almost one half of reported patients have died despite the use of several modalities of therapy. The remainder of patients improved over time, similar to the pattern of spontaneous disappearance of acquired FVIII inhibitors.

Case reports highlighting inhibitor features

An acquired IgG antibody isolated from the plasma of a female with systemic lupus erythematosus inhibited the activities of both plasma FXIII (tetramer) and platelet FXIII (dimer). Immunoelectrophoretically, no subunit A was detected in the patient's plasma or platelets, but the level of plasma subunit B was within reference range.⁷⁵

In an 80-year-old woman with an acquired bleeding disorder, an acquired IgG-l monoclonal antibody was detected using TEG and clot solubility tests. This acquired IgG-l monoclonal antibody selectively inhibited FXIIIa transamidation but did not inhibit thrombin-induced activation of FXIII.⁷⁶

An IgG antibody detected in a 62-year-old man using solubility of the patient's clot in 5M urea was associated with low reference range levels demonstrated by a putrescine casein incorporation assay (62%); however, on sodium dodecyl sulphate gel electrophoresis, none of the a chains and only two thirds of the g chains of fibrin became cross-linked. This IgG antibody recognized the plasma tetramer and inhibited virtually all a-chain and two thirds of g-chain cross-linking of fibrin, with a 100-fold greater affinity for the thrombin-activated forms of FXIII. A previously unreported effect of the antibody was seen, ie, the antibody induced an enzymatically active configuration in thrombin-activated FXIII, even in the absence of Ca²⁺.⁷³

A patient with Waldenström macroglobulinemia who was taking INH for tuberculosis developed an IgG antibody that was detected via a positive 5M urea solubility test result and low incorporation of monodansyl cadaverine into casein.⁷⁷

Another case report raises a concern as to whether a patient with psoriasis had an acquired FXIII inhibitor. Normalization of generalized bleeding and poor wound healing with improvement in joint mobility followed correction of a 19% activity of FXIII with replacement therapy.⁷⁸ In inherited severe FXIII deficiency, a minimal rise of FXIII activity to approximately the 3-5% range usually is sufficient to control bleeding. The higher FXIII activity of 19%, in this patient with psoriasis and bleeding, is reminiscent of the finding of residual FVIII coagulant activity in the plasma of patients with acquired FVIII inhibitors who also have bleeding out of proportion to the detectable residual FVIII activity. A summary by Lorand of the salient features of several patients with FXIII inhibitors is available.⁷⁹

WORKUP

Section 5 of 11  

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Lab Studies

• The following routine tests are the first step in the evaluation of any bleeding disorder: aPTT, PT, thrombin-clottable fibrinogen level, platelet counts, and bleeding time (the latter after ascertaining that the patient was not on antiplatelet drugs for at least the preceding 5 d). However, these tests cannot be used to screen for FXIII deficiency because the results would be within reference ranges in a patient with isolated severe FXIII deficiency.⁸⁰
• 5M urea solubility test: The next test performed is a qualitative screening test for severe FXIII deficiency that assesses clot solubility in 5M urea or 1% monochloroacetic acid. If the thrombin and Ca²⁺-induced clot lyses within a few hours, severe FXIII deficiency is suggested provided fibrinogen levels are qualitatively and quantitatively within reference range. Excluding hypofibrinogenemia and dysfibrinogenemia is important, since these conditions cause false-positive results on the 5M urea solubility test. The thrombin-clottable fibrinogen test can be used to exclude hypofibrinogenemia and dysfibrinogenemia.
• If the 5M urea solubility test demonstrates positive results, this finding should be confirmed by quantitating FXIII activity using a monodansylcadaverine or putrescine incorporation assay, which must be performed by laboratory personnel with expertise.
• TEG is an old method used to assess clotting and lysis of fresh whole blood, and it has been used as an early tool in the initial evaluation, and as a simple laboratory test, of the mechanical strength (effect of FXIII) of fibrin sealants.⁸¹ However, TEG cannot supplant any of the qualitative or quantitative tests discussed in this section.
• A new sensitive assay used to quantitate FXIII activity is based on monitoring the amount of ammonia (NH₃) released by using glutamate dehydrogenase and nicotinamide adenine dinucleotide phosphate during the transamidation reaction (cross-linking) by FXIII.
  
  
  • Reportedly, this test is sensitive over a wide range of activities, from a low of 1 U/L (0.1%) to a high of 470 U/L (47%), with an impressive coefficient of variation (CV) of less than 8%, even at very low FXIII activity levels. Note that a low CV in the low range of FXIII activity is a desirable feature of assays of this enzyme.⁸²
  • Compared to the cumbersome conventional quantitative amine incorporation assays, the new method appears to be simple, rapid, and reproducible not only in the assessment of inherited or acquired reductions of FXIII activity levels but also in the ability to measure increased FXIII activity levels resulting from certain mutations. The test fulfills the need for a simpler method to quantify FXIII activity.
  • The same group also has published results of a simple, quick (2 h), 1-step, enzyme-linked immunoassay (ELISA) to determine the presence of the plasma tetramer (A₂B₂). Results demonstrated high sensitivity and low CVs within batches and in day-to-day variations.⁸³
• Another new and sensitive colorimetric assay based on incorporation of 5-(biotinamido) pentylamine into fibrin/fibrinogen was compared to a photometric method based on ammonia release and an ELISA of FXIII subunit A to quantitate FXIII activity. The test was shown to be sensitive to both reductions and increases in activity; the increases resulted from the FXIII Val34Leu mutation.⁶⁸
• In addition, a₂PI and plasminogen activator inhibitor-1 assays should be performed to exclude abnormalities in the fibrinolytic pathway, which accelerate clot lysis.
• Sodium dodecylsulfate polyacrylamide gel electrophoresis under reducing conditions has been used to assess the presence of cross-linked g or a chains of fibrin, which is a reflection of FXIII activity. The studies must be performed by laboratory personnel with special expertise.
• If the presence of an inhibitor is suspected in a patient with a positive urea solubility test result, the next step is to repeat the urea solubility test with mixtures containing varying proportions of patient and normal plasma to differentiate between a deficiency or an inhibitor as the cause of a positive result. Since FXIII activity is present in serum, serum also may be substituted for plasma in the test.
• Semiquantitation of the susceptibility of the fibrin clot to fibrinolysis can be obtained by adding iodine-125-labeled fibrinogen, tissue plasminogen activator, thrombin, and Ca²⁺ to the patient's plasma, with measurement of the time to 50% clot lysis. This method is useful in evaluating inhibitors but must be performed by laboratory personnel with special expertise.
• See Lorand for a recent review of further details of the sequence of necessary testing to confirm the presence of a FXIII inhibitor.⁷³
• Acquired systemic disorders, including decompensated DIC and liver disease, require standard tests to confirm the diagnosis.
• Caution is warranted in obtaining blood samples for any coagulation assays from heparinized central lines because of the effect of large amounts of heparin on any coagulation test that depends on thrombin generation.
• Prenatal diagnosis
• • Use of several diagnostic procedures has been well established in the evaluation of patients with FVIII and factor IX (FIX) deficiencies. In one case report, a short tandem repeat marker that was closely linked to subunit A was used antenatally to identify the presence of a severe bleeding disorder in a subsequent pregnancy in a family in which an older sibling had severe FXIII deficiency.⁸⁴
  • Chorionic villous sampling at approximately 10-12 weeks of gestation or amniocentesis at 16-20 weeks of gestation can be performed to obtain fetal cells for DNA analysis or for linkage studies. If DNA analysis cannot be performed, fetal blood obtained by fetoscopy at approximately 20 weeks of gestation can be used. In general, these procedures carry risks ranging from a low of approximately 0.5% maternal-fetal complications to a high of approximately 1-6% fetal death for fetoscopy.
  • Perform these procedures only after intense genetic and obstetric counseling of the parents.
• Perform liver function tests; kidney function tests; HIV-1 and HIV-2 antigen and antibody tests; hepatitis A (HAV), hepatitis B (HBV), hepatitis C (HCV), hepatitis D, and hepatitis E antigen/antibody levels; and other tests as needed.
• Assess a-fetoprotein levels and other tumor markers as needed in patients with chronic hepatitis.

Imaging Studies

• MRI, CT scan, and ultrasound have been used to localize, quantify, and serially monitor the location and response of bleeding to specific therapy.
• Perform other imaging tests as needed to diagnose associated diseases.

Other Tests

• Perform ECGs as needed.

Procedures

• Diagnostic amniocentesis, chorionic villous sampling, or fetoscopy may be performed during pregnancy. Perform other routine procedures when indicated. Perform arthrocentesis only when infection is suggested. Any invasive procedure requires the appropriate factor replacement.
• When indicated, perform other procedures, such as colonoscopy, in persons without hemophilia. Evaluate persistent GI tract bleeding without an apparent cause using endoscopy and colonoscopy to exclude underlying lesions. Persistent genitourinary tract bleeding requires evaluation for nephrolithiasis, tumors, or obstruction. If a biopsy is needed, patients require replacement therapy prior to and following the procedure until the biopsy site has healed.
• Invasive lifesaving procedures should be performed in patients with inhibitors only in concert with appropriate treatment.

TREATMENT

Section 6 of 11  

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Medical Care

FXIII replacement is used to treat bleeding, to prevent perioperative bleeding during elective surgical procedures or, prophylactically, to prevent recurrent bleeding, as in CNS or joint hemorrhages. Serial monitoring of achieved FXIII levels is essential to document the adequacy of any therapy.

• Prompt and adequate therapy for acute bleeding is essential along with immobilization of the affected sites and pain relief. Most patients receive FFP or cryoprecipitate to treat bleeding. Information regarding the amount of FXIII present in either of these products usually is not available; therefore, monitoring the adequacy of FXIII levels is essential.
• Two intermediate-purity FXIII concentrates are being tested in the United States and are available in other countries.
• • Virus-inactivated FXIII concentrates made from human plasma or placenta are an improvement over traditional products.
  • Fibrogammin P (Centeon) is a plasma-derived virus-inactivated concentrate marketed in Europe, South America, South Africa, and Japan. It is available in the United States under a New Drug Application. A second FXIII concentrate (Bio Products Laboratory, Elstree, Hertfordshire, UK) is available on a per patient request.
  • No rFXIII product is currently commercially available in the United States.
• The long half-life of FXIII of 6-19 days and the hemostatic efficacy of even small amounts of FXIII of approximately 5% allow replacement therapy to be administered every 4-6 weeks. An FFP dose of 2-3 mL/kg may be effective for up to 4 weeks.^{85, 86} The dose of concentrate in adults with deficiency is 35 U/kg every 4 weeks.^{87, 88, 89}
• A paucity of data exists concerning the pediatric population. Hemostatic evaluation following a head trauma-induced large subcutaneous hematoma associated with recurrent postsurgical bleeding led to a diagnosis of severe FXIII deficiency in a 22-month-old boy. Following initial therapy, subsequent replacement with an FXIII concentrate dose of 50 U/kg every 5 weeks was sufficient to prevent rebleeding and allow healing.⁹⁰ Serial monitoring of actual levels achieved is important in children to determine adequacy of any therapy.
• Minor bleeding, as from cuts and abrasions, may respond to conservative measures, such as pressure, ice, and use of antifibrinolytic drugs. Avoidance of trauma and nonsteroidal anti-inflammatory drugs (NSAIDs) is helpful in reducing bleeding events.
• Several reports exist of the use of FXIII in unusual circumstances.
• • Effectiveness of normalizing FXIII levels in the treatment of a cerebrospinal fluid leak, which started 2 weeks after removal of a meningioma, was reported in a Japanese patient.⁹¹
  • The potential use of transglutaminases to mechanically stabilize and allow cultured epithelial autografts to take when used to repair extensive skin wounds supports a possible role of FXIII in the formation of de novo dermoepidermal junctions, thereby facilitating permanent skin replacement.⁹¹
  • Improved stability of surgical wounds has been reported following infusion of FXIII concentrates.
  • Although a few reports exist concerning the use of FXIII replacement in patients with scleroderma, Henoch-Schönlein purpura, and malignancies, the value of such replacement therapy remains to be established by proper clinical trials.^{6, 92, 93, 94}
• Patients with acquired inhibitors to FXIII should be treated using well-established principles of therapy.
• • FXIII dose depends on the characteristics of the inhibitor. One patient was treated preoperatively using a 10-fold dose of FXIII concentrate (350 U/kg) followed by a similar postoperative dose resulting in adequate hemostasis after coronary bypass graft surgery.⁸⁹
  • In addition to administering an FXIII concentrate whenever available, treat the underlying disorder and, when appropriate, use immunosuppressive agents, including the newer B-cell-directed monoclonal antibodies.
  • Note that spontaneous disappearance of acquired inhibitors is part of their natural history, and the use of milder less toxic immunomodulators, such as steroids, may suffice.
  • The proper choice of agent is dictated by clinical circumstances. Simple immediate ancillary measures of ice, pressure, ace wrap, immobilization of the affected joint, and avoidance of NSAIDs must not be forgotten.
  • The complexity of required treatment is exemplified by a patient with an INH-induced inhibitor in whom INH was discontinued, cryoprecipitate and FXIII concentrate were administered, the patient underwent plasma exchanges and treatment with an immunoadsorption column to reduce the inhibitor's titer, and immunosuppressives were administered before hemostatic success was achieved.^{75, 73, 77}
• To date, prophylactic factor replacement has been undertaken mainly in patients with intracranial bleeding or recurrent miscarriages caused by severe FXIII deficiency. Successful prevention of recurrent joint bleeds also has been accomplished using periodic transfusions of FFP and cryoprecipitate.⁵⁵ FFP can be administered in a dose of 2-3 mL/kg every 4 weeks.
• A literature review of bleeding risks and reproduction among patients with severe FXIII deficiency suggests that patients with clinically significant bleeding should start receiving factor replacement therapy in childhood to reduce early mortality from hemorrhages and to allow patients to reach adulthood. During pregnancy, monthly replacement was found to be effective in preventing miscarriages.⁹⁵ However, both short-term benefits and potential long-term adverse consequences of prophylactic use of these products must be discussed, with full patient participation in all decision making.
• Advances in the types of available products improve care. Addition of Tween 20 makes a reduction of the generation of soluble and insoluble aggregates of rFXIII possible when rFXIII is subjected to freezing and thawing or agitation.⁹⁶ Another advance in the technology relates to solving problems faced during freeze-drying and storing the dry solid. Improvement in storage stability of therapeutic proteins has obvious advantages for both storage and transport.⁹⁷
• Pooled plasma treated with solvent-detergent (PLAS+SD) is available to treat any condition in which FFP typically is used and for which no factor concentrate is available. Viral inactivation using the solvent-detergent (SD) process has been used in preparation of coagulation factor concentrates in the past. In vitro treatment of donor plasma with 1% of the solvent tri(n-butyl) phosphate (TNBP) and 1% of the detergent Triton X-100 leads to significant inactivation of a broad spectrum of lipid-enveloped viruses.
• • Studies of viral inactivation using the SD process show significant inactivation of the human pathogenic viruses hepatitis B and C and HIV. Other lipid-enveloped viruses (eg, Sindbis virus, bovine viral diarrhea virus) also have been used to monitor inactivation.
  • PLAS+SD is ABO blood type specific, and SD-treated plasma should be ABO compatible with the recipient's red cells.
  • The frozen product is supplied in 200-mL bags. Each 200-mL bag has been demonstrated to raise factor levels by approximately 2-3%, with 4-6 bags raising the factor level of a 70-kg person by approximately 8-18%.
  • Monitoring of specific factor levels before and after product infusion is important to ensure that hemostatically adequate levels are achieved and maintained to provide adequate hemostasis.
• Antifibrinolytic agents are not used commonly to treat patients with FXIII deficiency but may be used as ancillary therapy.
• • The hemostatic plug formed in the presence of adequate levels of FXIII at the time of surgical trauma (as with dental procedures or with mucosal bleeding) can be preserved by inhibiting fibrinolysis with e-aminocaproic acid (EACA; Amicar) or trans-p-aminomethyl-cyclohexane carboxylic acid (AMCA; also termed tranexamic acid; Cyklokapron) administered orally or, if needed, intravenously. EACA has been administered in a dose of 5 g orally or intravenously slowly prior to the surgical procedure, along with a dose of the appropriate FXIII replacement. This is followed by a maintenance dose of 1 g/h postoperatively until it is appropriate to start tapering the dose over the next several days.
  • AMCA is administered in a dose of 1.5 g intravenously every 6-8 hours and tapered, as needed; however, it is not available in the United States.
  • Antifibrinolytic agents also can be used as a mouthwash for oral bleeding and have been used to stop local intracavitary oozing.
  • Antifibrinolytic agents are contraindicated in patients with hematuria because of the possible risk of development of a firm occluding clot in the ureters when administered simultaneously with factor replacement. The drugs are not useful in the treatment of joint bleeding (see Factor VIII for more information).
• In recent years, the use of NSAIDs to relieve pain has increased in patients with bleeding disorders. Although they provide relief from inflammatory pain, patients experience increased GI tract or other bleeding because of the impact of the drugs on primary hemostasis, and they require additional FXIII replacement to control bleeding. The problem is magnified by the availability of over-the-counter NSAID pain relievers. Non-NSAIDs, such as acetaminophen and codeine-type analgesics, are much less effective, and some are addictive.
• Dental care: Routine dental care is of the utmost importance in maintaining dental hygiene.
• Other routine care, such as mammography in women older than 50 years or colonoscopy for patients older than 50 years, must be provided as in nonbleeding patients.

Surgical Care

All elective procedures require proper perioperative management.

• Patients with severe FXIII deficiency require FXIII replacement both preoperatively and postoperatively. Levels of as little as 3-5% may be sufficient to provide adequate hemostasis, and a single dose is sufficient to last several weeks unless excessive blood loss occurs. Serial factor levels must be performed to ensure adequacy of FXIII levels.
• Procedures such as endoscopies, although considered routine for unaffected individuals, require preprocedural product replacement so that patients do not bleed during or following a needed biopsy. Postbiopsy replacement must continue until the biopsy site has healed.
• Dental extractions or mucosal procedures can be handled using a single preprocedure dose of FXIII along with Amicar or AMCA. A standardized approach to dental extractions, as has been proposed for patients with hemophilia, may be used in patients with FXIII deficiency. Continuing antifibrinolytics on an outpatient basis for several days after a dental extraction is routine practice, with gradual tapering of dosage.
• Avoidance of NSAIDs and other platelet-inhibiting drugs perioperatively is essential to minimize bleeding risk. Ice packs and pressure are always useful when feasible.
• Application of fibrin glue as an ancillary measure is useful in helping control bleeding at surgical sites. Fibrin glue consists of a mixture of fibrinogen, thrombin, and FXIII used to cross-link freshly formed fibrin. Cryoprecipitate also has been used as a source of fibrinogen and FXIII, with the use of bovine thrombin to clot fibrinogen. Some preparations also incorporate antifibrinolytic agents to prevent clot lysis. In particular, fibrin glue has been useful in orthopedic surgery and with surgical procedures in patients with FXIII inhibitors. Bovine thrombin may elicit antibodies.
• Bleeding from suture holes is a complication in a variety of invasive vascular procedures (surgery, radiologic procedure, coronary angiography). In an experimental porcine vascular graft model, fibrin sealant containing FXIII effectively reduced blood loss and reduced the time to achieve adequate hemostasis more than fibrin alone or thrombin-coated gelatin sponges.⁹⁸

Consultations

• A hematologist, orthopedist, physical therapist, dentist, social worker, psychologist, infectious disease specialist, gastroenterologist/hepatologist, geneticist, and an appropriately equipped special laboratory all play important roles in providing optimal care for patients with FXIII deficiency and their families.
• The efforts of the National Hemophilia Foundation and its regional chapters must be recognized in helping to educate patients, assist service providers, foster dialog regarding problems and solutions among patients with bleeding disorders, and improve conditions for the entire community through support of legislation.

Diet

A healthy and nutritional diet should be encouraged.

Activity

Appropriate physical activity and physical therapy must be encouraged to maintain and preserve muscle function.

MEDICATION

Section 7 of 11  

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• Follow-up
• Miscellaneous
• Multimedia
• References

For FXIII replacement therapy, 2 intermediate-purity FXIII concentrates are being tested or are commercially available for use. FFP and cryoprecipitate also are used. An FFP dose of 2-3 mL/kg every 4 weeks has been used for replacement therapy under steady-state conditions. Dosing of cryoprecipitate is empiric, since no standardized amount of FXIII exists for cryoprecipitate. Repeat dosing should be guided by the adequacy of a prior dose as determined by FXIII assays. Currently, concentrates of FXIII are not commercially available in the United States.

PLAS+SD is ABO blood type specific. As a result of treatment with 1% tri(n-butyl)phosphate (or TNBP as the solvent) and 1% Triton X-100 (as the detergent), lipid-enveloped viruses (eg, HIV, HBV, HCV, Hantavirus, Marburg virus, Ebola virus) are disrupted and killed in significant numbers. The resulting fragments are inactive and cannot replicate or cause disease. PLAS+SD has proven efficacy in treating coagulation factor deficiencies when factor concentrate is unavailable. SD-treated plasma offers more protection to patients than is found in standard FFP. Patients with FXIII deficiency have been specifically treated successfully with PLAS+SD. Information regarding PLAS+SD can be found in the manufacturer's product circular.⁹⁹

Traditionally, FFP has been the source of factors for the treatment of coagulation factor deficiencies for which no concentrates are available; FXIII deficiency falls into this category.

Higher risks of virally transmitted illnesses remain among patients who are recipients of multiple units of FFP. The greater degree of viral safety assured by this treatment has led to the exclusive use of PLAS+SD instead of FFP in some countries (Norway and Belgium).

PLAS+SD delivers consistent and reproducible levels of coagulation factors. In contrast to the extreme variability in FFP, PLAS+SD contains no leukocytes, and physiologic inhibitor levels are mostly within reference range, with the exception of a moderate reduction in the levels of a₂ PI (approximately 0.48 IU/mL) and protein S (approximately 0.52 IU/mL). In addition, coagulation zymogens are not activated, reference range levels of other plasma proteins and immunoglobulins are present, and all lots have anti-HAV antibody levels greater than 0.8 IU/mL, providing passive administration of antibody that may neutralize HAV. PLAS+SD also lacks the largest vWF multimers and has proven efficacy in the treatment of a variety of bleeding disorders.

Disadvantages of PLAS+SD use include minor allergic reactions as observed with other blood products but that respond to antihistamines. PLAS+SD is contraindicated in patients with known IgA deficiency.

FXIII levels and efficacy of PLAS+SD: FXIII levels in 3 representative lots of pooled plasma (starting material prior to SD and other treatments) were 1.18 ± 0.05 U/mL (average ± standard deviation), with levels of 1.23 ± 0.06 U/mL in the final SD-treated, ultrafiltered, and sterile-filtered product.

Four patients with an inherited FXIII deficiency received successful prophylaxis with 1-2 U of PLAS+SD administered every 21-40 days on a total of 39 occasions over 42 months (range in each patient, 2-15 mo). PLAS+SD was proven to be equivalent to FFP in preventing hemorrhages in patients with known FXIII deficiency. A fifth patient with FXIII deficiency was treated successfully for soft tissue hemorrhages on an on-demand basis.¹⁰⁰

When PLAS+SD was stored at -18°C, FXIII activity was 1.14 ± 0.09 U/mL at the start and 1.33 ± 0.05 U/mL after 18 months of storage. Currently, based on additional data submitted, PLAS+SD has a US Food and Drug Administration (FDA)-approved 2-year shelf life according to F. Darr, MD, of the American Red Cross (Fred Darr, MD, e-mail, February 2002). Therefore, evidence exists that FXIII activity remains stable during long-term storage.

All PLAS+SD units that are administered should be ABO compatible with each patient's red cells. Adverse reactions include minor allergic reactions and volume overload. Rarely, citrate toxicity, hypothermia, and other metabolic problems arise if large volumes are used rapidly. Noncardiogenic pulmonary edema can occur. Antibody-induced positive results to the direct antiglobulin test and hemolysis also may occur rarely.¹⁰⁰

See t