Case of Perforating Osteoma Cutis

A 24-year-old man presented with a 1.5 × 0.5 cm-sized erythematous nodule with central crust on the forehead since 5 years ago. There was no history of trauma or previous skin disorders. Histopathologic examination showed a typical picture of osteoma cutis. In addition, transepidermal elimination of bony material was observed: red linear plate-like calcified lamella structures had extruded to the skin surface through the perforated epidermis. The perforating type of osteoma cutis was discussed.