Bartonella henselae Infection

Epidemiology

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• Etiology: Bartonella henselae (fastidious, intracellular Gram-negative bacillus).
• Transmission: Scratches, bites, or flea feces (Ctenocephalides felis) from domestic cats/kittens.
• Risk populations:
  • Cat-Scratch Disease (CSD): Immunocompetent individuals (most common in children and young adults).
  • Bacillary Angiomatosis (BA): Immunocompromised individuals (e.g., advanced HIV w/ CD4 < 100/mm³, transplant recipients).

Pathophysiology

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Clinical features

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• Cat Scratch Disease (CSD):
  • Primary lesion: Erythematous, non-tender papule/vesicle at scratch site 3–10 days post-exposure.
  • Regional lymphadenopathy: Axillary > cervical > epitrochlear 1–2 weeks later; tender, enlarged LNs (suppuration in ~10%).
  • Systemic: Low-grade fever, malaise, headache.
• Bacillary Angiomatosis (BA):
  • Cutaneous: Bright red/purple/violaceous, vascular papules or subcutaneous nodules; friable and bleed easily. c
  • Systemic: Fever, night sweats, weight loss in HIV/AIDS patient (CD4 < 100/mm³).
  • Visceral: Peliosis hepatis (cystic, blood-filled vascular spaces in liver/spleen), osteolytic bone lesions.
• Culture-Negative Endocarditis:
  • Subacute fever, heart murmur, embolic phenomena with persistently negative standard blood cultures.

Diagnostics

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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

Differential Diagnostics

• Kaposi Sarcoma: Caused by HHV-8. Differs by biopsy showing lymphocytic/plasma cell infiltrate with spindle cells, lacking neutrophils or positive silver stain.
• Pyogenic Granuloma: Solitary vascular lesion, usually follows trauma. Differs by lack of systemic symptoms or severe immunosuppression.
• Molluscum Contagiosum: Caused by Poxvirus. Differs by firm, non-vascular papules with central umbilication that do not bleed easily.
• Cherry Angioma: Benign vascular proliferation common in adults. Differs by non-friable nature, lack of systemic symptoms, and presence in immunocompetent pts

Treatment

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