Diagnostic Guidance for Cat Scratch Disease

Clinical Presentation

• Classic cat scratch disease presents with a papule or pustule developing 3-30 days after a cat scratch or bite, followed by regional lymphadenopathy about 3 weeks after inoculation 1, 2, 3
• Lymphadenopathy generally resolves within 1-6 months, with suppuration occurring in approximately 10% of cases 3
• Extranodal disease develops in ≤2% of cases 3

Diagnostic Algorithm

Step 2: Laboratory Testing

• Be aware of potential cross-reactivity between B. henselae and B. quintana 3

Step 3: Additional Diagnostic Methods

• PCR testing of tissue specimens can be valuable, especially in atypical presentations 3
• Warthin-Starry silver stain of infected lymph node tissue can confirm diagnosis, though it cannot differentiate Bartonella species 3

Treatment Considerations

• For patients >45 kg: 500 mg of azithromycin on day 1 followed by 250 mg for 4 additional days 3
• For patients <45 kg: 10 mg/kg of azithromycin on day 1 and 5 mg/kg for 4 more days 3