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 85–90% of patients with CSD and includes the following:
- ≥ 1 papule and/or pustule at the cutaneous site of inoculation
- 5–10 mm, erythematous, nontender
- Typically manifests 3–12 days after exposure
- Regional lymphadenopathy
- Swollen, tender lymph nodes 7–60 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
| Feature | Bacillary Angiomatosis (BA) | Kaposi Sarcoma (KS) |
|---|---|---|
| Etiology | Bartonella spp. (Bacteria) | HHV-8 (DNA Virus) |
| Histology | Capillary proliferation, plump endothelial cells | Spindle cells, slit-like vascular spaces |
| Infiltrate | Neutrophilic | Lymphocytic & Plasmacytic |
| Special Stain | Warthin-Starry stain shows organisms | N/A |
| Treatment | Antibiotics (Doxycycline, Erythromycin) | ART (first-line), Chemotherapy/Radiation for severe disease |