Osteogenesis imperfecta type IIA: evidence for dominant inheritance.

Thirty cases of radiologically proven type IIA osteogenesis imperfecta (OI) have been ascertained. All were isolated with 19 unaffected foreborn and 19 unaffected afterborn sibs. Two sets of parents, both Asian, were consanguineous. There was a significant parental age effect, most marked for paternal age. It is concluded that most cases of type IIA OI result from new dominant mutations.