Bacillary angiomatosis: causes, symptoms, diagnosis, treatment, and prognosis

Bacillary angiomatosis, also known as bacillary epithelioid angiomatosis or epithelioid angiomatosis, is an infectious disease that causes the proliferation of small blood vessels in the skin and internal organs. Bartonella henselae and Bartonella quintana can cause the disease. The incubation period of the disease is unclear and may be several years.


Causes

Bacillary angiomatosis mainly occurs in immunosuppressed patients, especially AIDS patients, with helper T lymphocytes often less than 50,000/L. This disease can also occur in other immunosuppressed hosts such as leukemia patients, and occasionally in HIV-negative patients without significant immunocompromised disease. In individuals with low immune function, local bacteria proliferate and can be transmitted by blood circulation, producing an angiogenic factor that stimulates vascular proliferation, resulting in characteristic angiomatoid lesions. Individuals with normal immune function are resistant to the proliferation of this bacterium and can develop granuloma and necrosis rather than angiomatoid lesions.


Signs and Symptoms

The disease occurs mostly in the process of HIV infection, but it can also occur in cancer patients and organ transplant recipients receiving chemotherapy, and rarely occur in normal persons. Most patients are males and may be associated with more HIV infection in males. 20% of patients have a recent history of cat scratches. Skin lesions are the most common symptom of this disease. The disease can also involve the liver, spleen, lung, bronchial mucosa, pleura, gastrointestinal mucosa, bone marrow, oral mucosa, and conjunctiva.

Skin lesions can be divided into dermal and subcutaneous lesions. Dermal lesions are red or dark red, pinhead sized papules, gradually enlarging into hemispherical or pedicled, elephantiasic nodules. Ulceration and serous exudation are present in the late stage. Skin lesions vary from single to multiple to hundreds or thousands in number, and can occur anywhere in the body. A single skin lesion on the face or hand can resemble a pyogenic granuloma, leaving mild pigmentation and induration after regression. Skin atrophy may occur after regression of large skin lesions. Generally, subjective symptoms are absent. Subcutaneous lesions are several centimeters in diameter plaques, often resembling cellulitis. Bone lesions under the skin lesions are common and may precede the skin lesions. Bone lesions mainly occur in the distal extremities, often with pain. X-ray examinations can reveal sharply demarcated osteolytic lesions, or poorly demarcated lesions with significant cortical destruction. Diffuse skin lesions are often accompanied by periosteal reactions.

Disseminated multiple organ infections are often accompanied by systemic symptoms such as fever and weight loss. Few patients can develop sepsis syndrome and bacteremia. Liver involvement can be manifested by peliosis hepatis, gastrointestinal symptoms, hepatomegaly, elevated serum transaminases, and elevated alkaline phosphatase. Liver biopsy reveals many blood-filled cysts in the liver and myxoid matrix and agglomerated granular purple materials in the lesions. In Warthin-Starry stain and electron microscopy, the granular materials are proved to be bacteria, which are the same as the bacteria in the skin lesions.

The natural course of bacillary angiomatosis is extremely varying, but for most patients, the lesions remain stable, or in the most common cases, the size and number of lesions gradually increase over time. The initial skin lesions are often the largest, and there are multiple satellite or disseminated skin lesions. If untreated, bacillary angiomatosis can cause death, and patients can die from visceral disease or impaired respiratory function caused by obstructive lesions.


Histopathology

The epidermis is flattened, superficial lesions may be similar to those of pyogenic granuloma, and the bilateral epidermis is inwardly curved. The small round blood vessels present with lobular hyperplasia, accompanied by a large number of endothelial cells protruding into the lumen. There may be cytoplasmic-rich and closely connected cuboidal endothelial cells, and irregular vacuoles appear in some cytoplasm, forming endothelioid appearance. The nuclei are hyperchromatic, oval or pleomorphic, and sometimes mitotic. Endothelial cell necrosis can occur in the center of the lobule of blood vessels. Massive neutrophil and eosinophil infiltrations between the proliferated endothelial cells are accompanied by obvious leukocytoclasis. The interstitial irregular purple granules can be clearly identified as agglomerated bacilli in Warthin-Starry stain.


Diagnosis

The diagnosis of bacillary angiomatosis is usually based on the typical lesion, histopathological changes, and bacteria found in the infected tissue.

Differential diagnosis

Pyogenic granuloma is with no neutrophil fragmentation, no nuclear dust, and no irregular purple granules composed of bacteria in histopathology.

Kaposi sarcoma presents with many angiogenesis in the dermis, significantly proliferated endothelial cells, spindle cells, vascular fissures, extravasated erythrocytes, and hemosiderosis in histopathology.


Treatment

Erythromycin 500mg 4 times a day or doxycycline 100mg twice a day can be selected for the treatment. Minocycline, tetracycline, clarithromycin, azithromycin, roxithromycin, and chloramphenicol may also be effective. Medications for prophylactic treatment are macrolide antibiotics or rifampicin. The duration of treatment depends on the extent of visceral involvement. For patients with only skin lesions or bacteremia, at least 8 weeks of treatment is required. For patients with visceral and bone involvement, 3 to 6 months or longer of treatment is recommended. Jarisch-Herxheimer reaction can occur after the first dose of antibiotics. Long-term antibiotics should be considered if patients still relapse after a significant course of treatment.


Prognosis

The prognosis of this disease is usually good, and the skin lesions in some patients can resolve spontaneously, but the mortality rate is high when systemic lesions occur.