[Congenital, plaque-like osteoma of the skin in an infant]

A plaque-like cutaneous osteoma in a male infant is described and compared with 12 remarkably similar cases from the literature. An important differential diagnosis is that of pseudohypoparathyroidism and it has to be excluded by the examination of the calcium and phosphorus metabolism. There are two possible explanations for the etiologie of osteoma cutis, an osseous hamartom, or a metaplasia of mesenchym cells. Because of some important reasons we prefer the hamartom concept.