RENPENNING SYNDROME MAPS TO XP11

Mutations in genes on the X chromosome are believed to be responsible for the excess of males among individuals with mental retardation. Suc h genes are numerous, certainly >100, and cause both syndromal and non -syndromal types of mental retardation. Clinical and molecular studies have been conducted on the Mennonite family with X-linked mental reta rdation (XLMR) reported, in 1962, by Renpenning et al. The clinical ph enotype includes severe mental retardation, microcephaly, up-slanting palpebral fissures, small testes, and stature shorter than that of non affected males. Major malformations, neuromuscular abnormalities, and behavioral disturbances were not seen. Longevity is not impaired. Carr ier females do not show heterozygote manifestations. The syndrome maps to Xp11.2-p11.4, with a maximum LOD score of 3.21 (recombination frac tion 0) for markers between DXS1039 and DXS1068. Renpenning syndrome ( also known as ''MRXS8''; gene RENS1, MIM 309500) shares phenotypic man ifestations with several other XLMR syndromes, notably the Sutherland- Haan syndrome. In none of these entities has the responsible gene been isolated; hence, the possibility that two or more of them may be alle lic cannot be excluded at present.