Posterior Auricular and External Auditory Canal Involvement from an Infected Preauricular Fistula Mimicking a First Branchial Cleft Cyst.

Preauricular fistula is a common congenital anomaly that typically presents with localized infection near the auricular pit. We report a case of an infected preauricular fistula in a 9-year-old girl presenting with atypical inflammation involving the posterior auricular sulcus and the external auditory canal, initially mimicking a first-branchial cleft anomaly. Despite prolonged antibiotic therapy, the infection persisted. Contrast-enhanced computed tomography suggested a branchial cleft lesion. However, intraoperative findings demonstrated that the fistulous tract terminated within the auricular cartilage without direct continuity to the posterior abscess cavity. Intraoperative and pathologic findings revealed that the infection had propagated through loose soft tissue planes rather than along a congenital epithelial tract. Staphylococcus lugdunensis was identified and is likely to have contributed to the aggressive clinical course. This case highlights a potential diagnostic pitfall and emphasizes the importance of correlating clinical, radiologic, and intraoperative findings for accurate diagnosis and appropriate surgical management.