Snapshot A 26-year-old woman presents to the urgent care clinic because of fever, weight loss, night sweats, and a red rash on her trunk, legs, and arms for the past week. She has a past medical history of HIV infection and currently is not on any anti-retroviral medications. She recently adopted a cat from the shelter 3 months ago and has been training it to not scratch when approached; however, she has been sustaining scratches during the training process. On physical exam, she has generalized lymphadenopathy and multiple clusters of violaceous papules and plaques. Her CD4 count is 100 cells/mm3. A skin biopsy was done and shows a neutrophilic infiltrate and granulomatous changes. Introduction Classification Bartonella henselae facultative intracellular, gram-negative rod transmission scratch or bite from a cat (more common) or dog clinical syndromes bacillary angiomatosis, a vasoproliferative disease benign capillary tumors of the skin immunosuppressed patients cat scratch disease tender lymphadenopathy bacterial endocarditis (culture-negative) Epidemiology incidence more common in the southern US demographics bacillary angiomatosis immunosuppressed patients cat scratch disease children and adolescents > adults risk factors HIV/AIDS immunosuppression cat scratch, bite, or lick Pathogenesis B. henselae replicates in red blood cells granulomatous inflammation mediated by CD4+ T-cells secretes γ-interferon and activates macrophages Associated conditions culture-negative bacterial endocarditis Prognosis cat scratch disease typically resolves within a few months bacillary angiomatosis typically resolves completely with treatment Presentation Cat scratch disease tender lymphadenopathy 2 weeks after exposure vesicle, wheal, or papule at site of trauma systemic symptoms low-grade fever myalgias fatigue Bacillary angiomatosis multiple clustered red or violaceous papules, plaques, or nodules on skin and mucosa bone pain systemic symptoms fever night sweats weight loss Studies Labs serologic detection of immunoglobulins via enzyme-linked immunosorbent assay (ELISA) or indirect immunofluorescence assay (IFA) detection of bacterial DNA on polymerase chain reaction (PCR) culture is not useful as the bacteria is fastidious and hard to culture Biopsy of skin lesions or lymph node neutrophilic infiltrate granulomatous changes Making the diagnosis based on clinical presentation and laboratory studies Differential Kaposi sarcoma distinguishing factor presents clinically similar to bacillary angiomatosis but biopsy reveals lymphocytic infiltrate Treatment Management approach cat scratch disease is self-limited and guidelines for antibiotics is unclear bacillary angiomatosis requires treatment with antibiotics Medical azithromycin indication cat scratch disease erythromycin or doxycycline indication bacillary angiomatosis Complications Persistent lymphadenopathy Aseptic meningitis Disfigurement