Distinct form of osteosclerosis in identical twins with mental retardation.

The osteoscleroses constitute a large and diverse group of disorders characterized by abnormally increased bone density present in either a diffuse or a focal pattern [1-3]. Etiology is generally obscure and classification is therefore based predominantly on the clinical features, particularly nadiognaphs and bone morphology [2, 4]. We describe a new osteosclenotic disorder, first manifesting in adult life in a set of mentally retarded, identical twins. This syndrome is characterized by a pattern of coincident osteosclenosis and osteopenia, and is associated with mildly elevated serum alkaline phosphatase. We also compare this disorder with other osteosclerotic syndromes.