Giant skull vault defect in a child caused by Langerhans cell histiocytosis: the "calvaria-eating disease".

Langerhans cell histiocytosis (LCH) is a rare disease of young children that can be difficult to diagnose and treat. Clinical manifestations can sometimes be quite unusual, and bony lesions can reach a large size before treatment is sought. We present a unique case of a 3-year-old male child with a painless giant calvarial defect and cystic swelling. Complete removal of the cyst with curettage of the involved bone margins and cranioplasty was done using bone cement (polymethyl methacrylate, PMMA). However, there was a flare up of the disease due to abnormal inflammatory reaction to PMMA, and cranioplasty bone flap had to be removed. The child did well after PMMA bone flap removal.LCH should be suspected in a male child presenting with a large calvarial defect and no history of trauma. The use of materials, viz., hydroxyapatite, poly-DL-lactide (PDLLA), and PMMA for cranioplasty in LCH, may cause reactivation of the disease process and therefore must be used cautiously in these patients.