Makindo Medical Notes

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📖 About Cat Scratch Disease (CSD)

• Caused by Bartonella henselae, a Gram-negative, facultative intracellular bacillus.
• Transmitted after a cat bite, scratch, or lick on broken skin 🐾.
• Common cause of chronic lymphadenopathy in children.
• Usually benign and self-limiting in immunocompetent individuals, though symptoms may persist for 1–5 months.

🧬 Aetiology

• Transmission: Cat scratches/bites or cat saliva into wounds.
• Organism: B. henselae requires host ATP and grows only in cell culture.
• Reservoir = domestic cats (especially kittens); vector = cat fleas (Ctenocephalides felis).

🩺 Clinical Features

• Typical presentation:
  • Initial papule/pustule at inoculation site.
  • Regional lymphadenopathy within 1–2 weeks (often axillary, cervical, or epitrochlear).
  • Low-grade fever, malaise.
• Atypical/systemic disease (esp. children & immunocompromised):
  • Prolonged fever, hepatosplenic involvement.
  • Parinaud’s oculoglandular syndrome 👁️ (conjunctivitis + preauricular lymphadenitis).
  • Neurological: encephalitis, seizures, coma (rare).
  • Musculoskeletal: osteomyelitis, arthropathy.
  • Dermatological: erythema nodosum.
  • Immunocompromised: bacillary angiomatosis (vascular skin lesions) or peliosis hepatis.

🧾 Differential Diagnosis

• Tuberculosis (scrofula).
• Lymphoma / leukaemia.
• Toxoplasmosis.
• Atypical mycobacterial infection.
• Viral infections (EBV, CMV).

🔍 Investigations

• Histology: Granulomatous inflammation ± necrosis; Warthin–Starry silver stain shows organisms.
• Serology/PCR: Detection of Bartonella antibodies or DNA (where available).
• Blood tests: ESR ↑, mild neutrophilia, thrombocytopenia possible.
• Imaging: Ultrasound/CT in systemic disease (hepatic/splenic lesions).

💊 Management

• Supportive: Analgesia, antipyretics. Most cases resolve spontaneously.
• Antibiotics:
  • Indicated in systemic disease, severe lymphadenitis, or immunocompromised patients.
  • Doxycycline = first-line.
  • Alternatives: Azithromycin (well tolerated, esp. in children), Ciprofloxacin, Chloramphenicol.
• Surgical: Rarely needed; avoid excision of lymph nodes (risk of sinus formation). Drainage if suppuration occurs.
• Prolonged therapy: 4–6 months in severe or relapsing systemic disease.

💡 Clinical Pearl

📌 Exam trigger: Child with cat exposure + papule + tender lymphadenitis. 📌 Usually benign, but immunocompromised → think of bacillary angiomatosis. 📌 Avoid unnecessary surgery; most resolve with time ± antibiotics.

📚 References

• Cat Scratch Disease – Iowa State University
• Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases.