Rubinstein-Taybi syndrome: further evidence of a genetic aetiology.

Two families are described with Rubinstein-Taybi syndrome. In one family the syndrome is seen in its full form in the index case and his uncle; three cousins of the index case also show varying degrees of expression of the disorder. In the other family a brother and sister are affected. This case report illustrates the varying expression of the disorder and the change in facial appearance with age. A polygenic basis of inheritance is supported and it is suggested that the typical facial appearance in infancy is the best means of identifying the disorder, as broad thumbs and toes may not be apparent or may be only a borderline abnormality.