A 36-year-old man from Uganda presents with a painless lump in the right posterior thigh for 2 weeks, associated with low-grade fever and mild anorexia. Two years previously, he had been diagnosed with human immunodeficiency virus (HIV) infection. He had never taken antiretroviral therapy and had no history of opportunistic infections. His current CD4+ lymphocyte count was 7 cells/mm3.
He had lived in the United States for 8 years working as a housekeeper in a home with pet cats. He drank socially, did not smoke, and denied intravenous drug use, trauma, recent travel, and tuberculosis exposure. He had not been sexually active for many years.
On examination, a solid nontender mass was present in the right posterior thigh. Computed tomographic scan of the right leg showed an enhancing soft tissue mass in adductor magnus, with a second focus in rectus femoris. Magnetic resonance angiography (Fig. 1) showed a highly vascular mass within the adductor muscle group, with satellite lesions consistent with intramuscular lymph nodes.
What is your diagnosis?
Diagnosis: Bacillary angiomatosis with pyomyositis.
Biopsy of the thigh mass revealed skeletal muscle infiltration by nodules of vascular proliferation, fibroblastlike cells, a mixed inflammatory infiltrate, and small capillaries with prominent endothelial cells. No abnormal mitoses or overt cellular atypia were present. Warthin-Starry silver staining showed occasional aggregations of bacteria within vascular nodules. DNA extracted from tissue was subjected to polymerase chain reaction using primers specific for Bartonella species. Electrophoresis was performed, and a band at 586 base pair indicated the presence of Bartonella DNA. Further analysis was consistent with Bartonella quintana.
Bartonella species are weak gram-negative bacilli, better visualized with Warthin-Starry silver or Giemsa stains. They have several characteristics in common: they can cause prolonged bacteremia in humans and other mammals; they may be transmitted by arthropod vectors, such as lice and fleas; they cause angioproliferative lesions; and they grow reasonably well in blood cultures but are difficult to subculture on solid media or to grow from tissue samples.
Invasion of vascular endothelium may be crucial for Bartonella pathogenicity. Bartonella species may promote angioproliferation by secreting soluble proteins. Bartonella-infected monocytes and macrophages may also contribute to angioproliferation via paracrine secretion of vascular endothelial growth factor and interleukin 1β.1 Bartonella species also prolong the survival of vascular endothelial cells by inhibiting several stages in apoptosis.2
Bartonella species have overlapping presentations. The first recognized species, Bartonella bacilliformis, is geographically restricted to the Andes Mountains and causes an acute febrile illness, Oroya fever, sometimes followed by chronic, vascular, warty skin lesions or verruga peruana. Bartonella henselae is the usual cause of the fever and lymphadenitis of catscratch disease. Bartonella quintana causes a relapsing febrile illness, trench fever, with body lice as the major vector. In immunocompromised patients, B. Quintana and B. Henselae cause bacillary angiomatosis, a disseminated infection with a broad spectrum of clinical manifestations, including friable vascular skin nodules, vascular lesions of the liver and spleen (peliosis hepatis et splenis), bacteremia, osteomyelitis, and rarely pyomyositis.3-5 There is at least 1 previous report of Bartonella pyomyositis without cutaneous lesions, as in this case.5
Pyomyositis in HIV patients, as in non-HIV patients, is usually caused by Staphylococcus aureus.6 In this case, both the vascular proliferation noted on magnetic resonance angiography and the history of cat exposure suggest the unusual diagnosis of Bartonella pyomyositis. Both B. Henselae and B. quintana are epidemiologically linked to cats.7
Macrolides and tetracyclines are commonly used for the treatment of bacillary angiomatosis. Although the optimal duration of treatment is unknown, weeks to months of therapy are recommended in HIV patients.3 This patient was treated with clarithromycin (500 mg, twice daily) for 8 weeks. Of note, highly active antiretroviral therapy was begun approximately 1 month into his treatment for bacillary angiomatosis. The thigh mass regressed and had completely resolved by the end of therapy.
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2. Kirby J, Nekorchuk DM. Bartonella-associated endothelial proliferation depends on inhibition of apoptosis. Proc Natl Acad Sci U S A.
3. Daly J. Bartonella species. In: Gorbach SL, Bartlett JG, Blacklow NR, eds. Infectious Diseases.
3rd ed. Philadelphia: Lippincott Williams & Wilkins; 2004:1843-1850.
4. Whitfeld MJ, Kaveh S, Koehler J, et al. Bacillary angiomatosis associated with myositis in a patient infected with HIV. Clin Infect Dis.
5. Husain S, Singh N. Pyomyositis associated with bacillary angiomatosis in a patient with HIV infection. Infection.
6. Crum NF. Bacterial pyomyositis in the United States. Am J Med.
7. La VD, Tran-Hung L, Aboudharam G, et al. Bartonella quintana
in domestic cat. Emerg Infect Dis.