Eosinophilic Granuloma of the Thumb Presenting in a 4-Month-Old Child: Case Report and Review of the Literature.

Eosinophilic granuloma (EG) is a benign bone tumor of unknown origin usually seen in children. It is typically found in flat and long bones of the skull and of the appendicular skeleton, respectively. Small bones are rarely affected. The diagnosis and treatment of EG can be challenging as differential diagnosis includes several disorders that can cause osteolytic lesions. Moreover, surgical treatment can be difficult due to the small size of the bone and surrounding structures. Here we describe a case of EG of the proximal phalanx of the thumb (P1 D1) presenting in a 4-month-old boy with persistent swelling and limited range-of-motion of the interphalangeal joint in the left thumb. Over a 6-year follow-up, no sign of relapse was observed. Moreover, the curetted bone did regenerate, and it appeared homogenously dense as normal trabecular bone on the last plain radiographs; the patient was symptom-free at the last follow-up visit. Clinical presentation, treatment, pathoanatomy, localization, and complication of this form of tumor are discussed, and all previously reported cases are reviewed to give a more comprehensive picture of EG of the hand and fingers.