Cat-scratch disease

• Definition: a benign, self-limiting infectious disease that is transmitted mainly by cats (via scratching, biting, or licking) 
• Epidemiology: predominantly affects children and adolescents
• Pathogen: Bartonella henselae (gram negative, aerobic bacillus) 
• Clinical features
• General: malaise, loss of appetite, fever
• Localized
• One or more 5–10 mm large, erythematous, nontender cutaneous papules or vesicles develop approx. 3–10 days after exposure at the site of inoculation. 
• Swollen, tender lymph nodes 7–60 days following exposure 
• Develops as primary lesions disappear
• Usually unilateral, occasionally suppurative
• Most commonly involves lymph nodes of axillae, neck, or groin (nearest the site of inoculation)
• Resolves after 2–4 months
• In immunocompromised individuals (e.g., patients with HIV) Bacillary angiomatosis (red-purple papules that bleed easily)
• Hepatic peliosis: a benign vascular condition characterized by multiple blood-filled cysts and vascular sinuses in the liver
• Can be asymptomatic or cause abdominal pain, jaundice, and/or liver failure
• In rare cases, cysts may rupture, causing intraperitoneal hemorrhage
• Bacteremia and endocarditis
• Diagnostics
• Bacterial culture from blood, swabs, or lymph node aspirate
• Antibody testing 
• Histological study
• 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.
• Differential diagnosis: Kaposi sarcoma (has lymphocytic infiltrate as opposed to bacillary angiomatosis)
• Treatment
• Mild or moderate cases: azithromycin (5-day course) to decrease lymphadenopathy and the duration of illness 
• In the case of persistent and/or disseminated disease (e.g., bacillary angiomatosis): erythromycin OR doxycycline
• In the case of CNS involvement or endocarditis: rifampicin PLUS either erythromycin OR doxycycline

References

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