Bacillary angiomatosis (BA) is most often caused by infection with Bartonella henselae or Bartonella quintana, gram-negative rods that stimulate the proliferation and migration of endothelial cells. Trauma from cats, such as cat scratches, bites, or licks, have been associated with B henselae infection, whereas being undomiciled and body louse infestation have been associated with B quintana infection. Rare cases of BA due to Bartonella elizabethae and Bartonella vinsonii (associated with canine exposure) have also been reported. BA is primarily seen in HIV-infected individuals with a CD4+ count of <100 cells/µl. It has been reported in patients immunocompromised by malignancy, immunosuppressive therapy, solid organ transplantation, and hepatitis B infection; it may very rarely occur in immunocompetent patients. It is rare in children.

BA is characterized by cutaneous angiomatous papules and nodules. Other cutaneous lesions include lichenoid plaques, subcutaneous nodules, and ulcers. Organisms may disseminate systemically, in which case cutaneous lesions may be accompanied by fever, malaise, and night sweats. Multiple internal organs – including the liver (known as bacillary peliosis hepatis), spleen, bone (lytic bone lesions often under cutaneous lesions, resulting in bone pain), lung (endobronchial nodules and pulmonary infiltrates), central nervous system (CNS), cerebral masses, cardiac (endocarditis), and gastrointestinal (GI) tract – may then be involved.

Upon appropriate treatment, cutaneous lesions resolve with some hyperpigmentation or scarring.