What is the appropriate management and first‑line antibiotic regimen for an otherwise healthy patient with mild, localized cat‑scratch disease lymphadenopathy?

Management of Mild, Localized Cat Scratch Disease

For otherwise healthy patients with mild, localized cat scratch disease lymphadenopathy, azithromycin is the first-line antibiotic when treatment is indicated, though most cases are self-limited and may not require antibiotics at all. 1, 2

Clinical Context and Natural History

Cat scratch disease typically presents with a papule or pustule developing 3-30 days after cat exposure, followed by regional lymphadenopathy approximately 3 weeks after inoculation. 1 The lymphadenopathy generally resolves spontaneously within 1-6 months, with suppuration occurring in only about 10% of cases. 1 Most cases in immunocompetent hosts are self-limited and do not require antibiotic therapy for resolution. 3

When to Treat vs. Observe

The majority of mild, localized cat scratch disease cases in normal hosts do not require anti-infective therapy. 3 However, antibiotic treatment may be considered to accelerate recovery and reduce lymph node size more rapidly. 4, 3

First-Line Antibiotic Regimen

When antibiotics are chosen, azithromycin has been shown in placebo-controlled studies to speed recovery and is associated with more rapid diminution in size of infected lymph nodes. 3

Azithromycin Dosing:

• For patients >45 kg: 500 mg on day 1, followed by 250 mg daily for 4 additional days (total 5 days) 1, 2
• For patients <45 kg: 10 mg/kg on day 1, followed by 5 mg/kg daily for 4 additional days 1, 2

Alternative Antibiotic Options

For patients who cannot tolerate azithromycin or when alternative therapy is needed, the following options have demonstrated clinical efficacy:

• Doxycycline (with or without rifampin) 5, 2
• Rifampin 3
• Ciprofloxacin 3
• Trimethoprim-sulfamethoxazole 3
• Clarithromycin 3

Critical Pitfalls to Avoid

Do not confuse cat scratch disease (Bartonella henselae infection causing lymphadenopathy) with infected cat scratch wounds (polymicrobial wound infections). These are distinct clinical entities requiring different management:

• Infected cat scratch wounds require amoxicillin-clavulanate as first-line therapy for coverage of Pasteurella multocida and other wound pathogens 2, 6
• Cat scratch disease (the lymphadenopathy syndrome) is treated with azithromycin when antibiotics are indicated 1, 2

Diagnostic Confirmation

Diagnosis is typically based on:

• History of cat exposure (scratch or bite, especially from kittens) 1
• Compatible clinical presentation with regional lymphadenopathy 1
• Serologic testing showing elevated IgG antibodies to B. henselae (>1:64 titer) or positive IgM 1, 7
• PCR testing of tissue specimens can be valuable in atypical presentations 1

Monitoring and Follow-Up

• Lymphadenopathy should gradually decrease over weeks to months 1
• Suppuration occurs in approximately 10% of cases and may require needle aspiration (not incision and drainage) 1
• Patients with fever and elevated C-reactive protein should be evaluated for systemic complications including splenic abscess, hepatic abscess, or other extranodal disease 7
• Systemic involvement occurs in approximately 2% of cases overall but may be higher in certain populations 1, 7

Special Populations

For immunocompromised patients, maintain a lower threshold for antibiotic initiation and be vigilant for atypical presentations including bacillary angiomatosis and disseminated disease. 2 These patients may require more aggressive and prolonged antibiotic therapy.