Epidermoid Cyst in the Lacrimal Sac Region Presenting as Acute Dacryocystitis.

Infected epidermoid cysts in the medial canthus can clinically mimic acute dacryocystitis, posing diagnostic challenges. The authors report the case of a 13-year-old male with a 2-month history of recurrent right medial canthal redness, swelling, pain, and purulent discharge. Initially misdiagnosed with acute dacryocystitis at another institution, he experienced symptom recurrence despite multiple incisions and drainage attempts. A comprehensive evaluation in our department, including history, physical exam, computed tomography dacryocystography, ultrasonography, and lacrimal endoscopy, was performed. The definitive diagnosis of an infected medial canthal epidermoid cyst was established histopathologically, followed by successful surgical management. This case underscores the principle that infection in the lacrimal sac region is not synonymous with dacryocystitis, emphasizing the necessity of a thorough, multidimensional diagnostic approach to prevent misdiagnosis and ensure timely, appropriate treatment.