X-linked mental retardation without physical abnormality: Renpenning's syndrome.

A number of families have been reported in which mental retardation appeared to be segregating as an X-linked recessive (Martin and Bell, 1943; Allan, Herndon, and Dudley, 1944; Losowsky, 1961; Renpenning et al, 1962; Dunn et al, 1962/1963; Neuhauser et al, 1969; Snyder and Robinson, 1969; Neuhauser and Zerbin-Rudin, 1970). We reported 5 such families (Turner, Turner, and Collins, 1971b) in which the moderately retarded males were distinguished by the fact that they showed no physical abnormality. The first family in which X-linked mental retardation was associated with a similar lack of physical stigmata in the affected males was described by Renpenning et al (1962) and a similar family study was later published by Dunn et al (1962/1963). On the basis of the observations that the affected males in these families showed no physical stigmata the histories of a group of moderately retarded males without physical stigmata were examined and it was found that 60% has either an affected brother or a family history compatible with an X-linked entity. It was proposed therefore that the absence of physical abnormality in a moderately retarded male was suggestive of an X-linked form of mental retardation and the eponym of Renpenning's syndrome was suggested (Turner et al, 1971b). In order to obtain substantiation of this observation the brother pairs with mental retardation in an institution were ascertained and their families were studied.