Epidemiology

Etiology

• Pathogen: B. henselae (gram-negative, aerobic bacillus)
  • Primarily occurs via animal (most commonly cat) scratches, bites, and saliva exposure

Pathophysiology

Clinical features

Localized CSD

Uncomplicated localized disease occurs in 85�?0% of patients with CSD and includes the following:

• �?1 papule and/or pustule at the cutaneous site of inoculation
  • 5�?0 mm, erythematous, nontender
  • Typically manifests 3�?2 days after exposure
• Regional lymphadenopathy
  • Swollen, tender lymph nodes 7�?0 days after exposure
  • Usually unilateral
  • Most commonly involves lymph nodes proximal to the site of exposure in the axilla, neck, or groin
  • Occasionally suppurate
• Constitutional symptoms: fever (may be prolonged), malaise, myalgias, loss of appetite

Extranodal CSD

• Bacillary angiomatosis
  • Seen primarily in immunocompromised patients (especially patients with AIDS and/or CD4 count < 100)
  • Solitary or multiple, red, flesh-colored or colorless papules and nodules that bleed easily
  • Fever, chills, malaise, anorexia

Diagnostics

Biopsy

• Lymph nodes
  • Warthin-Starry staining of the involved lymph node may show clusters of rod-shaped bacteria.
  • H&E staining of cutaneous lesions may show necrotizing granuloma formation and neutrophilic infiltrate.
• Bacillary angiomatosis
  • Benign capillary vascular proliferation
  • Neutrophilic infiltrate
    • Neutrophilic inflammation is seen in bacillary angiomatosis. Lymphocytic inflammation is seen in Kaposi sarcoma.
  • The Warthin-Starry stain is used to visualize bacilli

Treatment