Plate-like osteoma cutis: nothing but skin and bone?

Osteoma cutis encompasses a group of cutaneous ossifying disorders, more commonly secondary to trauma, inflammation or neoplasms. Fourteen per cent, however, are primary, and these may be syndromatic (associated to Albright's hereditary osteodystrophy) or occur in isolation. We report a case of a 10-year-old girl who presented with a stone-hard plate on the scalp, with no relevant personal or family history, nor changes in calcium-phosphate metabolism, parathyroid hormone or thyroid function. Skin biopsy confirmed osteoma cutis. Plate-like osteoma cutis is rare, and believed to be a non-progressive form of heterotopic ossification, included in the spectrum of progressive osseus heteroplasia and Albright hereditary osteodystrophy, due to GNAS gene mutations. This recently clarified association should remind us of the possible unfavourable evolution of a seemingly innocent clinical picture, emphasising the need for appropriate evaluation, management and follow-up.