Orbital dermoid cyst presenting as chronic osteomyelitis.

A dermoid cyst is a choristoma that arises from the displacement of ectoderm to a subcutaneous location along embryonic closure lines. Rarely dermoids have a deep intraorbital component that is connected to a superficial component through a defect in bone, also known as dumbbell dermoid. We report the case of a young boy who was misdiagnosed having chronic osteomyelitis of the zygoma, based on the clinical and radiological features. On surgical exploration he was found to have a dumbbell-shaped dermoid with a bony defect. Histopathological features were consistent with a diagnosis of dermoid cyst with chronic inflammation.