AUTHOR AND EDITOR INFORMATION

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• Introduction
• Clinical
• Differentials
• Workup
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• Medication
• Follow-up
• Miscellaneous
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INTRODUCTION

Section 2 of 11  

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

Background

Porphyria is a predominantly inherited metabolic disorder, resulting from a deficiency of an enzyme in the heme production pathway and overproduction of toxic heme precursors. Eight different enzymes are involved in the pathway, and deficiencies of the second to eighth enzyme result in a family of disorders with various, and often overlapping, clinical presentations.

The 2 types of porphyrias are divided by the following predominant symptoms: (1) the neurovisceral or acute porphyrias with abdominal pain, neuropathy, autonomic instability, and psychosis, and (2) the cutaneous porphyrias with symptoms of photosensitive lesions on the skin.

Aminolevulinic acid dehydrase (ALAD) porphyria and acute intermittent porphyria (AIP) cause predominately neurovisceral symptoms, whereas congenital erythropoietic porphyria (CEP), porphyria cutanea tarda (PCT), and erythropoietic porphyria (EP) cause mostly cutaneous symptoms. Two porphyrias overlap these categories, and can cause both neurovisceral and cutaneous symptoms, namely hereditary coproporphyria (HCP) and variegate porphyria (VP).

Only the cutaneous manifestations of the porphyrias are considered here. For explanation of diagnosis and management of the acute porphyrias and the acute manifestations of porphyrias with both neurovisceral and cutaneous components, please refer to the companion article Porphyria, Acute.

Some of the confusion with reference to the porphyrias is derived from the many synonyms for each particular disorder (see Table 1 below).

Table 1. Cutaneous Porphyria and Synonyms

PCT is the most common porphyria in the United States and Europe. Its manifestations are prototypical of the cutaneous porphyrias. Cutaneous lesions independent of acute attacks are experienced by 50% of patients with VP, whereas cutaneous manifestations of HCP occur with acute attacks. CEP and EPP have onset in infancy. CEP lesions are a more severe form of PCT lesions. EPP lesions are milder than PCT lesions but may approach PCT lesions in severe cases. HEP is a rare homozygous form of PCT that presents in childhood.

Pathophysiology

An outline of the porphyrin pathway demonstrates the pathophysiological mechanisms that cause porphyria.

Biosynthesis of 1 heme molecule requires 8 molecules of glycine and succinyl-coenzyme A (CoA). Heme is essential in many critical biochemical functions. For example, oxygen binding and transport, mixed-function oxidation in the cytochrome P-450 pathway, activation and decomposition of hydrogen peroxide, oxidation of tryptophan and prostaglandins, and the production of cyclic guanosine monophosphate (cGMP) cannot occur without heme. The liver produces approximately 15% of the body's heme, and the remainder is produced in the bone marrow. Heme produced in the liver is primarily used to produce cytochromes and peroxisomes, and heme produced in the bone marrow is primarily used for hemoglobin synthesis and oxygen transport.

As demonstrated in Image 1, enzymes are located in either the mitochondria or the cytosol.

Delta-aminolevulinic acid (ALA) synthase is the first step in the heme biosynthesis pathway. This enzyme condenses glycine and succinyl-CoA and has 2 isoforms that are encoded by separate genes; the housekeeping isoform is expressed in all tissues, whereas the erythroid isoform is expressed only in hematological tissue.

• ALA synthase is the rate-limiting step for heme production in the liver but not the bone marrow. Indeed, the erythron responds to stimuli for heme synthesis by increasing cell numbers.
• In the liver, ALA dehydratase and porphobilinogen (PBG) deaminase levels typically are low, resulting in ALA and PBG accumulation with increased ALA production under normal conditions.
• High ALA levels induce heme oxygenase, increase bilirubin production, and inhibit ALA synthase.
• Heme inhibits ALA synthase synthesis, mitochondrial transfer, and catalytic activity in the liver. This leads to tight control of ALA production because ALA synthase turnover is rapid.
• Exogenous chemicals can induce ALA synthase by depleting existing heme or inhibiting heme synthesis. The 3 common mechanisms for this include the destruction or enhanced production of cytochrome P-450 heme and rapid inhibition of ferrochelatase.
• In contrast to the liver, heme increases the synthesis of hemoglobin and ALA synthase in the bone marrow. In addition, erythroid ALA synthase is not affected by exogenous chemicals.

ALA dehydratase condenses 2 molecules of ALA to form the monopyrrole PBG ALA dehydratase, which is inhibited by lead, levulinic acid, hemin, succinylacetone, and alcohol.

• Lead displaces zinc from the enzyme. This inhibition can be reversed completely by supplemental zinc or dithiothreitol.
• Succinylacetone, a substrate analogue of ALA that is found in the blood and urine of patients with hereditary tyrosinemia, is the most potent inhibitor of ALA dehydratase.

PBG deaminase catalyzes the polymerization of 4 molecules of PBG in a head-to-tail orientation, yielding a linear tetrapyrrole intermediate, hydroxymethylbilane. The tissue and erythrocyte isozymes are encoded by the same structural gene.

Uroporphyrinogen III cosynthase forms uroporphyrinogen III from hydroxymethylbilane by reversing the orientation of the last pyrrole ring before cyclizing the linear molecule. Uroporphyrinogen I cosynthase forms uroporphyrinogen I from hydroxymethylbilane by cyclizing the linear molecule without modifying any of the pyrrole rings. Normal tissues contain an excess of uroporphyrinogen cosynthases compared to PBG deaminase.

Uroporphyrinogen decarboxylase sequentially removes a carboxylic group from the acetic side chains of each of the pyrrole rings to yield coproporphyrinogen. This enzyme has highest affinity for uroporphyrinogen III. It is inhibited by several metals, including copper, mercury, and platinum, but the evidence indicating that iron has an effect on this enzyme is controversial.

Coproporphyrinogen oxidase removes a carboxyl group from the propionic groups on 2 of the pyrrole rings to yield protoporphyrinogen IX.

Protoporphyrinogen oxidase forms protoporphyrin by removing 6 hydrogen atoms from protoporphyrinogen IX. This enzyme has been identified in human fibroblasts, erythrocytes, and leukocytes. It is inhibited noncompetitively and irreversibly by hemin.

Iron is inserted into protoporphyrin by ferrochelatase as the last step in the heme synthesis pathway. Enzyme activity is stimulated by fatty acids and is inhibited by metals, such as cobalt, zinc, lead, copper, and manganese, as well as by metalloporphyrins.

Porphyria cutanea tarda

Porphyrin overproduction occurs in the liver and the skin. Singlet oxygen, which is the primary toxic agent in the photodermatoses of porphyria, is the high-energy form of oxygen in which all the outer shell electrons are paired. It is generated by visible light (400 nm) in the presence of photosensitizers, such as the various porphyrins. Abnormally high complement, polymorphonucleocytes, and prostaglandins occur in lesions.

Erythropoietic protoporphyria

Mechanisms are similar to PCT, except that locally cutaneous production of porphyrins probably does not occur.

Congenital erythropoietic porphyria

Bone marrow is the primary site of the enzyme defect. Conspicuous porphyrin-laden normoblasts and reticulocytes are found in the marrow. Photolysis of porphyrin-laden erythrocytes occurs in the dermal capillaries, causing subepidermal lesions. Repeated trauma causes secondary skin changes and results in joint contractures. An intrinsic erythrocyte abnormality results in autohemolysis.

Splenomegaly occurs as a consequence of the removal of damaged and hemolyzed erythrocytes. Cholecystitis results from porphyrin-rich gallstones. Bone marrow hyperexpansion results in fragile bones.

Frequency

United States

The absence of a porphyria registry in the United States impedes an accurate calculation of frequencies, but the overall prevalence is estimated as 4 per 100,000. However, as indicated in Table 2, the porphyria incidence also varies significantly by type, with PCT being the most common and CEP being very rare. The lack of recognition of these disorders may contribute to inaccurate knowledge of their true incidence.

Despite earlier reports, the frequency of the genetic defect and phenotypic expression have a moderately strong relationship. A highly variable penetrance rate has been noted. Expression of the genetic defect is more common in familial cases, suggesting that such families may have an additional undetected genetic abnormality or environmental exposure. Around one half of individuals with genetic defects are symptomatic.

International

In general, porphyrias do not have a geographic preference. However, certain porphyrias have a high incidence in certain parts of the world (see Table 2).

PCT type I (ie, sporadic) is more common than PCT types II and III (ie, familial) in Europe, South Africa, and South America; however, the reverse is true in North America. Incidence of HCP is particularly variable with race. Incidence of VP is particularly high in South Africans of Danish descent.

Table 2. Frequency Varies with the Specific Porphyria

Mortality/Morbidity

CEP is associated with a significant decrease in life expectancy.

Race

See Table 2.

• PCT does not have a racial predilection except in South Africa, where it is more prevalent among Bantu persons. This is believed to be caused by a higher incidence of hemosiderosis in these individuals.
• Incidence of HCP is highly dependent on race.
• VP has a particularly high incidence in South African persons of Dutch descent.

Sex

Most porphyrias do not demonstrate a sex predilection (see Table 2).

• A change to a nearly equal sex distribution is attributed to the higher rate of alcoholism in males combined with the recent increase in the use of estrogens by women. Both these factors exacerbate manifestations of the porphyrias.
• The sex predilection of HCP varies with race (see Table 2).

Age

• CEP and EP usually present in infancy, but manifestations can be delayed until childhood. CEP can cause hydrops fetalis and recurrent fetal loss.
• HCP has a variable age of onset but usually does not present before adolescence. However, cases have been reported at younger ages.
• Symptoms of PCT and VP most often manifest in adulthood. However, inheritance of 2 abnormal genes can cause onset in childhood. Childhood onset is more unusual for VP than PCT, and, in the case of PCT, onset in infancy has been reported. Because PCT has a relatively high prevalence and low penetrance, 2 asymptomatic carriers each can transmit an abnormal gene without knowledge of the existing abnormality. HEP represents the onset of homozygous PCT type II in childhood.

CLINICAL

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History

PCT, HCP and VP usually manifest after the second decade, and skin symptoms are chronic and appear several days after sun exposure. Increased fragility, blistering, and scarring are noted, especially over the back of the hands. Remission may occur in the winter months, if sunlight exposure is decreased.

EEP typically presents in early childhood, and skin symptoms arise immediately after sun exposure with burning, edema, and erythema.

The presence of neurologic symptoms and abdominal pain, in association with cutaneous symptoms, would favor VP or HCP as the likely underlying porphyria.

PCT is associated with several precipitating factors.

• Alcoholism
• Iron overload (eg, in transfused patients with thalassemia)
• Hemochromatosis or HFE locus mutations
• Dialysis
• Estrogen
• Hepatitis C virus (HCV), cytomegalovirus (CMV), and HIV infection

Physical

Skin changes are the hallmark of the cutaneous porphyrias. They can be acute (EP) with erythema, edema, and erosions that eventually lead to facial scarring, or more chronic (PCT, VP, HCP), with skin fragility, blistering, and scarring, often over the backs of the hands.

• Congenital erythropoietic porphyria
• • Diaper - Pink- or dark-stained urine
  • Cutaneous lesions
    • Subepidermal bullous lesions that worsen with exposure to sunlight
    • Hyperpigmented or hypopigmented healing subepidermal lesions
    • Epidermal atrophy
    • Pseudoscleroderma
    • Mutilation of facial skin and cartilage
  • Hair - Hypertrichosis, alopecia
  • Eyes - Keratoconjunctivitis, vision loss
  • Musculoskeletal
    • Resorption of distal phalanges
    • Contractures
    • Decreased range of motion
    • Pathological fractures
    • Vertebral compression and collapse
    • Osteolytic and sclerotic lesion
  • Growth - Shortness of stature
  • Abdomen, splenomegaly, upper right quadrant tenderness, positive Murphy sign
• Porphyria cutanea tarda
• • Cutaneous lesions
    • Vesicle and bullae formation occurs in areas exposed to light, including the dorsum of hands and face.
    • Legs and feet commonly are involved in women.
  • Secondary skin changes from vesicular and bullous lesions.
    • Skin fragility with erosion from mild shearing trauma
    • Hyperpigmentation or hypopigmentation of areas exposed to light
    • Melanosis and violaceous-brown discoloration in areas exposed to light
    • Milia
    • Pseudoscleroderma
    • Atrophy and scaring of healed skin
    • Alopecia
    • Dystrophic calcification
    • Nonhealing ulcerations
  • Light urticaria is rarely seen.
  • See the Dermatology Online Atlas for images of cutaneous lesions.
  • Hair - Hypertrichosis develops slowly.
• Erythropoietic protoporphyria - Skin signs
• • Exposure to light, especially in the spring and summer, causes cutaneous stinging and burning followed by erythema and edema.
  • Petechiae, purpura, vesicles, and crusting may develop.
  • Lesions similar to those of PCT may be seen in severe sun exposure but are much less common.

Causes

• Table 3. Causes by Type of Porphyria
  

  Porphyria	Deficient Enzyme	Location	Inheritance	Chromosome Band
  CEP	Uroporphyrinogen III synthase	Cytosol	AR	10q25.3-26.3
  PCT	Uroporphyrinogen decarboxylase	Cytosol	AD	1p34
  HEP	Uroporphyrinogen decarboxylase	Cytosol	AR	1p34
  HCP	Coproporphyrinogen oxidase	Mitochondrial	AD	3q12
  VP	Protoporphyrinogen oxidase	Mitochondrial	AD	1q22-23
  EPP	Ferrochelatase	Mitochondrial	AD, AR	18q22

• CEP is associated with uroporphyrinogen III cosynthase activity of about 40% normal activity.
• PCT type II and type III are inherited, whereas type I occurs spontaneously. Type I and type III are localized defects in liver enzyme activity, whereas type II involves a defect in both the liver and erythrocyte enzymes. Overall, 80% of affected individuals have PCT type I. Type II affects approximately 20%, and type III affects 5% of individuals. Familial PCT has about a 10% penetrance rate.
• Expression of the disorder is precipitated by many factors, including the following:
• • Alcoholism
  • Beta-thalassemia major
  • Diabetes mellitus
  • Dialysis
  • Estrogen
  • HCV, CMV, and HIV infection
  • Hematologic malignancy
  • Hemochromatosis
  • Hepatocellular carcinoma
  • Lupus erythematosus
  • Renal failure
• HEP is considered the homozygous form of PCT type II and is associated with a 75% decrease in enzyme activity in all tissues.

DIFFERENTIALS

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Other Problems to be Considered

Halogen hydrocarbon exposure

WORKUP

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Lab Studies

• Demonstration of elevated porphyrins in plasma (particularly for CEP), urine, and stool are very useful for diagnosis of the porphyrias.
• Qualitative urine examination can identify urine porphyrins. However, normal urine contains porphyrins, making comparison with a control sample essential. In both the amyl alcohol and talc tests, the urine must be adjusted to a pH of 4 by mixing 3 mL of urine with 1 mL of 1 mol/L acetate buffer.
• • For the amyl alcohol test, 4 mL of amyl alcohol is added to the 4-mL buffered urine solution. After vigorous shaking or low-speed centrifuge, the mixture is examined under a Wood lamp. A pink-to-red fluorescence in the upper organic layer indicates a positive result.
  • For the talc test, 100 mg of talc is added to 10 mL of the buffered urine solution and shaken vigorously. Low-speed centrifuge for about 10 minutes produces a talc pellet, which can be examined under a Wood lamp. A pink or red color indicates a positive result.
• Protoporphyria can be diagnosed by identifying numerous fluorescent erythrocytes in blood examined microscopically with a 100-watt iodine-tungsten lamp.
• Qualitative stool studies can help guide the diagnosis.
• • Mix 1-2 g of stool in 2 mL of an amyl alcohol, glacial acetic acid, and ether mixture.
  • Red fluorescence under a Wood lamp indicates that porphyrins are present.
• Stool porphyrin levels that are combined with other laboratory values and clinic correlation help guide the diagnosis. However, levels of porphyrins are highly variable, and, in most cases, exact values for each disorder have not been established.
• Table 4. Quantitative Fecal Porphyrins by Type of Porphyria

  Porphyrin Type	CEP	PCT	HCP	VP	EPP
  Uroporphyrin	Significantly increased	Increased	Within reference range	Within reference range	Within reference range
  Coproporphyrin	Significantly increased	Increased	Significantly increased	Increased	Within reference range
  Protoporphyrin	Within reference range	Within reference range	Increased	Significantly increased	Significantly increased

• Quantitative urine porphyrin levels can be useful, but prior qualitative urine testing is desirable.
• • Although HCP and VP have identical urine porphyrin profiles, stool porphyrin testing can differentiate them.
  • CEP and PCT also have identical porphyrin patterns; however, erythrocyte examination results are positive only for CEP.
• Table 5. Quantitative Urine Porphyrins
  

  Porphyrin type	CEP and PCT	HCP and VP
  5-Aminolevulinate	Within reference range	Significantly increased
  PBG	Within reference range	Significantly increased
  Uroporphyrin	Significantly increased	Increased
  Coproporphyrin	Increased	Significantly increased

• Hematopoietic testing
• • Iron overload is almost always present in PCT and is reflected by abnormally high serum iron levels, low total iron-binding capacity, and high serum ferritin levels.
  • Hemolytic anemia with polychromasia, poikilocytosis, anisocytosis, and basophilic stippling is observed in CEP.
  • Thrombocytopenia and leukopenia are observed if hypersplenism develops in CEP.
• Functional enzyme assays are not widely available and, therefore, are not commonly used in cutaneous porphyria diagnosis. ALAD and AIP assays are useful, and, at specialized centers, assays for other cutaneous porphyria types (eg, coproporphyrinogen oxidase) may be available. While these other enzyme assays may be available, differential tissue expression of the enzymes makes these assays less useful in some individuals and they are not reliable for diagnostic purposes.
• Many genetic defects responsible for porphyria have been identified. However, in general, a large number of defects account for each porphyria type, limiting the practical use of these tests. For example there are 121 mutations in the PPOX gene that leads to VP. In the future, advances in microarray technology may make routine DNA testing possible. Currently, genetic testing is useful in 2 situations, as follows:
• • First, if a genetic defect is known to be present in an individual, family members can be tested for the defect.
  • Second, certain ethnic groups have a high incidence of a particular mutation. For example, many South African families demonstrate a specific mutation for VP.

Imaging Studies

• Imaging studies have no direct value.

Procedures

• Skin biopsy is not routinely indicated for the diagnosis of cutaneous porphyria and may lead to further scarring and poor healing.

Histologic Findings

Porphyria cutanea tarda

Skin lesions examined under light microscopy demonstrate subepidermal bullae with dermal papillae at the bases, elastosis and periodic acid-Schiff (PAS)-positive vessels in the dermis, and acid mucopolysaccharides at the dermal-epidermal junction. Immunofluorescence reveals accumulation of immunoglobulin G (IgG) and immunoglobulin M (IgM) and complement around dermal vessels and at the dermal-epidermal junction.

Liver tissue demonstrates siderosis, fatty changes, necrosis, chronic inflammatory changes, and granuloma formation. Red autofluorescence and needlelike inclusion bodies also are observed. Cirrhosis and neoplastic changes are not uncommon.

TREATMENT

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Medical Care

• Iron depletion can treat several of the cutaneous porphyrias. High plasma iron levels inactivate uroporphyrinogen decarboxylase, the enzyme deficient in PCT, and induce 5-aminolevulinate, a major regulatory enzyme in the heme biosynthetic pathway. Thus, the activity of the deficient enzyme is reduced further and porphyrins that cannot be metabolized are produced in increased quantities. Iron depletion also induces the synthesis of porphyrin pathway enzymes. In addition, iron overload resulting from chronic renal failure, a condition not uncommonly seen in association with PCT, is improved by this therapy.
• • Phlebotomy and apheresis can remove excessive iron in patients with PCT. Standard phlebotomy for adults consists of removal of 250-500 mL of blood once or twice per week. The patient's tolerance and clinical response regulate the exact amount. In patients with chronic renal failure, more frequent small-volume phlebotomies and high-dose erythropoietin combined with phlebotomy, are effective.
  • Monthly neocyte red blood cell exchange transfusions are reportedly useful in PCT, VP, and EPP.
  • Erythropoietin is reportedly effective in PCT. By stimulating erythrogenesis, excess iron stored is mobilized and a drop in serum iron, ferritin, and plasma porphyrins is observed. Combining higher doses of erythropoietin with phlebotomy is effective in patients with renal failure.
  • Deferoxamine forms a stable complex with iron, thereby preventing it from entering into further chemical reactions in PCT and CEP. Long-term therapy slows hepatic iron accumulation and retards progression of hepatic fibrosis. Iron is chelated from ferritin and hemosiderin but not from transferrin, cytochromes, or hemoglobin. The chelate readily passes through the kidney, giving the urine a characteristic reddish color.
  • Iron oxidizes vitamin C, causing patients with iron overload to become deficient in vitamin C. Vitamin C supplements also increase the availability of iron.
• Toxic metabolites have deleterious effects. Porphyrin levels can be reduced by direct methods or with medications that bind porphyrins. These methods are useful adjuncts to iron load reduction therapy, or when such therapy is ineffective or limited because of comorbid conditions, such as severe renal disease.
• • Therapeutic erythrocytapheresis has been combined with plasma exchange to reduce uroporphyrin blood levels. The procedure is continued until urine uroporphyrins are less than 600 mcg/d.
  • Chloroquine and hydroxychloroquine, 2 antimalarial medications, chelate and remove hepatic-bound porphyrins by forming water-soluble complexes that are eliminated in the urine.
  • Cholestyramine is a polymeric resin that binds bile acids to form a nonabsorbable complex, which is excreted unchanged in the feces. This compound also binds carboxylated porphyrins excreted in the bile. By preventing enterohepatic circulation, porphyrins do not reenter the systemic circulation.
• Oral photoprotection can be achieved with free radical scavengers, thereby reducing free radicals, singlet oxygen formation, and the photosensitizing effect of porphyrins.
• • Beta-carotene is a pigment found in various green and yellow fruits and vegetables and can decrease the severity of photosensitivity reactions in patients with porphyria. Beta-carotene does not alter stool concentrations of protoporphyrins, and plasma or erythrocyte concentrations are not affected. Laboratory evidence suggests that beta-carotene quenches free radicals and singlet oxygen, which are produced when porphyrins are exposed to light and air. Carotenodermia (yellowing of the skin) usually develops after 4-6 weeks and coincides with the start of photoprotection. Protection decreases within 1-2 weeks after discontinuation of therapy. Plasma concentrations of 4-6 mcg/mL are therapeutic for most patients.
  • Cysteine was found to reduce photosensitivity in patients with protoporphyria. Cysteine is believed to inactivate free radicals. Cysteine is a precursor to glutathione, a free radical scavenger.
  • N-acetylcysteine has been used, but the efficacy is questionable. Recent studies have used N-acetylcysteine in PCT elicited by HIV, HCV, and hemodialysis with some benefit.
• Sunscreen protection agents should be used if sun exposure is expected. Sun E45 lotion sun protection factor (SPF) 15 and Sun E45 cream SPF 25 have superior ultraviolet (UV)-A and blue light protection than Report onCarcinogens (RoC) 15+A+B, while all have good UV-B protection for photosensitive patients with EPP. In general, sun-blocking creams containing titanium dioxide or zinc oxide are useful. Sunless tanning agents that impart a pigment to the stratum corneum, especially those containing dihydroxyacetone, can also help.
• Acute scleritis in PCT is treated with indomethacin or systemic steroids when standard treatment does not improve the condition.

Surgical Care

• Many anesthetics can exacerbate porphyria, requiring an experienced anesthesiologist for proper treatment during surgery.
• Cholecystectomy may be required for severe cholelithiasis in CEP.
• Splenectomy may be required if severe hemolytic anemia develops in CEP.
• CEP has been cured with allogenic bone marrow transplant. Risks of this procedure must be carefully considered.
• EPP is not curable with liver transplant, although combined liver and bone marrow transplant may be curative in the future.

Consultations

• Contact a porphyria expert to assist in diagnosis and management of short-term and long-term treatments. Because porphyria spans many disciplines, experts may be certified in the area of metabolic disease, gastroenterology, or hematology.
• A hematologist may be particularly helpful if phlebotomy, apheresis, or exchange transfusion procedures are being used. In addition, management of deferoxamine and erythropoietin therapy also may require such an expert. A hematologist should be consulted if bone marrow transplant or splenectomy is considered for CEP.
• Seek dermatologist consultation for management of cutaneous lesions.
• Seek ophthalmologist consultation if ocular manifestations arise.
• Gynecologist consultation may be necessary for menses control because estrogens should be avoided.
• Anesthesiology consultation is necessary before sedation of minor procedure or surgery.

Diet

A high-carbohydrate diet can reduce disease severity. A low-carbohydrate diet is strictly forbidden.

Activity

• Contact with direct sunlight should be minimized. Sunscreen protection should be used when skin is exposed to the sun.
• Shading of glass windows in cars can minimize light exposure during driving.
• Activities that could damage skin lesions should be avoided.

MEDICATION

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Drug Category: Iron-depleting agents

Iron depletion therapy improves uroporphyrinogen decarboxylase activity, reduces the induction of 5-aminolevulinate synthase, and induces synthesis of porphyrin pathway enzymes in patients who have PCT with normal renal function. Patients with chronic renal failure should be treated further for iron overload resulting from chronic transfusion therapy.

Drug Category: Porphyrin-reducing agents

Several compounds can chelate or bind porphyrins.

Drug Category: Nonsteroidal anti-inflammatory drugs (NSAIDs)

Inflammation of the sclera can be reduced by strong anti-inflammatory medications.

FOLLOW-UP

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Further Outpatient Care

• Patients on antimalarial medications are at risk for ophthalmological and central visual dysfunction, peripheral neuropathy, deafness, and blood dyscrasias.
• • Periodic ophthalmologic examinations including visual acuity and slitlamp, funduscopic, and visual field tests should be performed.
  • Periodically evaluate reflexes and muscular strength.
  • Hearing should be objectively tested periodically.
  • Periodically check complete blood cell count.
• Cholestyramine can cause vitamin K deficiency. All patients on long-term therapy should be examined for bleeding or bruising and should receive supplemental vitamin K.

Deterrence/Prevention

• Probably safe medications: Many medications can induce or worsen porphyria (see Table 7), while others have not been associated with worsening porphyria (see Table 6). Furthermore, many medications have not been tested in patients with known porphyria. The list below is not exhaustive, and any medication used in a patient with porphyria should be researched.
• A more extensive list of safe drugs is available at the University of Queensland Porphyria Research Unit web site.
• Table 6. Medications Likely to be Safe for Patients with Porphyria
  

  Acetaminophen	Adrenaline	Amitriptyline
  Aspirin	Atropine	Bromides
  Chloral hydrate	Chlordiazepoxide	Colchicine
  Diazepam	Digoxin	Diphenhydramine
  EDTA	Ether	Glucocorticoids
  Guanethidine	Ibuprofen	Imipramine
  Indomethacin	Insulin	Labetalol
  Lithium	Methylphenidate	Naproxen
  Narcotics	Neostigmine	Nitrous oxide
  Penicillamine	Penicillin	Phenothiazines
  Procaine	Propranolol	Succinylcholine
  Tetracycline	Thyroxine	Tubocurarine

• Potentially unsafe medications: Many medications induce or worsen acute and cutaneous porphyria. Many of these medications are metabolized, at least to some extent, by the liver. Liver metabolism may induce the cytochrome P-450 enzymes that require heme, thus inducing heme production. Other medications sensitize the skin to solar damage. Only common medications are listed below, and any medication used in a patient known to have porphyria should be investigated. In addition, many medications have not been used for patients with porphyria, thus the potential for worsening porphyria is not known. The list below is a guide for determining if a medication could have triggered a porphyria reaction.
• A more extensive list of safe drugs is available at the University of Queensland Porphyria Research Unit web site.
• Patients should refrain from alcohol ingestion, estrogen use, and iron supplementation.
• Table 7. Medications that are Potentially Unsafe for Use in Patients with Porphyria

  Alfaxalone	Alkylating Agents	Antipyrine
  Arthrotec	Barbiturates	Busulfan
  Butalbital	Carbamazepine	Carisoprodol
  Chlordiazepoxide	Chloroquine	Clonidine
  Danazol	Danocrine	Dapsone
  Diclofenac	Ergot	Erythromycin
  Erythropoietin	Estrogens	Ethchlorvynol
  Fluroxene	Griseofulvin	Heavy metals
  Hydralazine	Ketamine	Mafenide
  Meprobamate	Methoxsalen	Methyldopa
  Metoclopramide	Nitrazepam	Nortriptyline
  Pargyline	Pentazocine	Phenazopyridine
  Phenobarbital	Phenoxybenzamine	Phenylbutazone
  Phenytoin	Plaquenil	Porfimer
  Primidone	Progestins	Pyrazinamide
  Ranitidine	Rifampin	Spironolactone
  Succinimides	Sulfonamides	Sulfonylureas
  Theophylline	Tolazamide	Tranylcypromine
  Valproate

Complications

• CEP is associated with splenomegaly, hypersplenism, and cholelithiasis.
• PCT is associated with an increased incidence of hepatocellular carcinoma and cirrhosis.
• EPP is associated with cholelithiasis in a significant number of cases. Severe liver disease may develop as a result of periportal fibrosis and cirrhosis, leading to death in 20% of cases. Rapidly progressive liver failure associated with accelerating photosensitivity and cholestasis can occur and is accompanied by abdominal pain, splenomegaly, and hemolysis.

Prognosis

• CEP is associated with a significantly decreased lifespan, whereas the other cutaneous porphyrias are associated with morbidity from the complications of skin lesions.

Patient Education

• The following web resources are useful for patient reference and education.
• • American Porphyria Foundation
  • Canadian Porphyria Foundation
  • European Porphyria Initiative
  • National Institute of Diabetes & Digestive & Kidney Diseases
  • National Organization for Rare Disorders
  • Online Mendelian Inheritance in Man
  • University of Queensland Porphyria Research Unit

MISCELLANEOUS

Section 9 of 11  

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

Medical/Legal Pitfalls

• Infectious agents, such as HCV and HIV, can elicit PCT. Failure to identify these associated disorders can lead to unnecessary morbidity. Although HCV and HIV can cause increases in porphyrins by themselves, they cannot cause porphyria unless the individual is genetically predisposed.
• Carefully review drugs that exacerbate porphyria before prescribing medication. Many medications do not appear on the lists of safe and unsafe drugs, indicating that they may not have been used with patients who have porphyria; such medications should be used with much caution. In addition, the safety of many medications listed in Table 6 and Table 7 is based on few cases, limiting the generalized application of this information.
• A pseudoporphyria syndrome can be elicited by exposure to hexachlorobenzene. Failure to identify a pseudoporphyria can lead to inappropriate treatment.
• Symptoms caused by exposure to various industrial chemicals and the disorder of multiple chemical hypersensitivities have been blamed on porphyria. Little evidence supports this notion. Most of the evidence indicates that any symptomatology is caused by the industrial toxin or underlying disorder.

MULTIMEDIA

Section 10 of 11  

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

Media file 1:  The heme production pathway. Heme production begins in the mitochondria, proceeds into the cytoplasm, and then is resumed in the mitochondria for the final steps. This figure outlines the enzymes and intermediates involved in the porphyrias. Enzymes names are presented in the boxes. Names of the intermediates are outside the boxes, between arrows. Multiple arrows leading to a box demonstrate that multiple intermediates are required as substrates for the enzyme to produce one product.
	View Full Size Image
Media type:  Graph

REFERENCES

Section 11 of 11

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

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Article Last Updated: Oct 4, 2006