Abstract
The etiology of posterior auricular swelling can be infectious, congenital, oncologic, or autoimmune. The most common cause of swelling in this region is reactive lymphadenopathy. Among the infectious etiologies, Bartonella henselae is an often-overlooked cause in immunocompetent individuals due to its varied clinical features. This swelling may fail to resolve despite the use of standard antibiotics, thereby presenting a diagnostic challenge for clinicians. We present a healthy nine-year-old male with no significant medical history who presented with persistent, painful postauricular swelling for 12 days following treatment for streptococcal pharyngitis. Despite a full course of antibiotics, the swelling progressed to a fluctuant mass with overlying redness. Further history revealed recent kitten exposure and a healed scratch on the right forearm, which raised suspicion of cat scratch disease (CSD). Comprehensive physical examination showed a hypopigmented healed scar on the right distal forearm and a posterior auricular abscess, which was drained and cultured. The diagnosis was confirmed by elevated Bartonella henselae serology with an IgM titer of 1:80 (reference range <1:20) and an elevated IgG antibody titer of 1:512 (reference range <1:64). Azithromycin was initiated due to serologic confirmation and the presence of suppuration, leading to resolution within three weeks. This case conclusively highlights the importance of considering CSD in children with unilateral lymphadenitis unresponsive to standard antibiotics, emphasizing the value of detailed history and physical examination in the primary care setting.