Bartonella henselae

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