Excerpt from Bacillary Angiomatosis

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Background

Bacillary angiomatosis (BA) is the vascular proliferative form of infection with Bartonella organisms. Bacillary angiomatosis was first described in 1983 in a patient infected with the human immunodeficiency virus (HIV). Subsequently, it has been described in patients following organ transplants and in immunocompromised persons. It is occasionally reported in patients who are immunocompetent. Initially, bacillary angiomatosis was called epithelioid angiomatosis because of its histological appearance.

In 1990, Relman et al identified a visible but uncultivable bacillus from affected tissues using molecular methods. They concluded that the unique 16S gene sequence associated with epithelioid angiomatosis belonged to a previously uncharacterized microorganism, most closely related to Rochalimaea quintana. Later, the same organism was recovered in specialized culture media. The gram-negative organism was later named Rochalimaea henselae, and, in 1993, Rochalimaea was reclassified under the genus Bartonella. Bartonella henselae and Bartonella quintana each have been cultured from and detected in bacillary angiomatosis tissues. Bacillary angiomatosis is the second most common angiomatous skin lesion in patients infected with HIV.

Pathophysiology

B henselae and B quintana are small gram-negative rods in the family Bartonellaceae. Bartonella, Rickettsia, Ehrlichia, and Afipia species all are part of the alpha-2 subgroup of the alpha-proteobacteria.

Bacillary angiomatosis may affect almost any organ system, although it most commonly affects skin and subcutaneous tissue. Subcutaneous lesions may erode into underlying bones (ie, osseous bacillary angiomatosis), especially the tibia, fibula, and radius. Involvement of ribs and vertebrae has been described. Rarely, skeletal muscles may be involved, resulting in pyomyositis. Mucous membranes of the conjunctiva and upper airway and perineum (anus and penis) may be affected. Bacillary angiomatosis may be accompanied by disseminated visceral disease (peliosis), mainly in the liver (peliosis hepatis), spleen, and lymph nodes.

Other internal organs that may be involved include the brain, bone marrow, heart, lungs, pleura, larynx, oropharynx, tongue, esophagus, stomach, duodenum, colon, peritoneum, diaphragm, kidneys, adrenal glands, pancreas, uterine cervix, and vulva. Extrinsic compression of the common bile duct by enlarged peripancreatic, celiac, and portohepatic nodes has been reported.

The pathogenesis of bacillary angiomatosis includes early blood-borne dissemination of organisms. Bartonella organisms readily attach to and may enter erythrocytes. They avoid opsonization and host phagocytosis by unknown mechanisms and become persistent within the intravascular compartment. An angiogenic factor may be responsible for the vascular proliferation observed in patients with bacillary angiomatosis because a similar factor mediates vasoproliferation in verruca peruana, the second stage of Bartonella bacilliformis infection.

Cutaneous lesions result almost equally from B henselae and B quintana infections. However, subcutaneous and osseous lesions usually are caused by B quintana infection. Visceral involvement is almost exclusively caused by infection with B henselae. Neurological disorders are associated more frequently with B quintana infection than with B henselae.

Domestic cats (Felis domesticus) are the reservoirs of B henselae, which may be transmitted by cat bites or scratches or, potentially, by bites from cat fleas (Ctenocephalides felis). Kittens are more frequently associated with transmission of B henselae than older cats. Humans appear to be the only reservoir of B quintana; the human body louse, Pediculus humanus, is the transmission vector.

Frequency

United States

The exact incidence of bacillary angiomatosis is not known. Cases of bacillary angiomatosis have been reported in almost all states, especially in Florida, Texas, New York, and northern California (San Francisco area), areas of high HIV prevalence.

International

Relatively fewer cases of bacillary angiomatosis are reported from Europe compared to North America, which may imply that either diagnoses are missed or a minimal reservoir of bacilli exists in Europe. Cases have also been reported from Africa, Peru, and Argentina.

Mortality/Morbidity

The exact mortality and morbidity of bacillary angiomatosis is not known because the condition was described only recently.

Race

Approximately 40% of US patients with bacillary angiomatosis are white, 40% are black, and 20% are of Hispanic origin.

Sex

Approximately 90% of US patients with bacillary angiomatosis are men, probably because a disproportionate number of patients infected with HIV also are men.

Age

Bacillary angiomatosis is extremely rare in children but was reported in a 12-year-old boy with acute leukemia who was undergoing chemotherapy and also in a 6-year-old girl who was immunocompetent.

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