Mental Retardation, X-Linked, Syndromic 9

Clinical Features

Shrimpton et al. (1999) reported a large 3-generation family in which 11 males had severe mental retardation associated with microcephaly and variable short stature. Speech was severely delayed. Testicular size was normal.

Mapping

By linkage analysis, Shrimpton et al. (1999) identified a candidate disease locus, which they termed MRXS9, on chromosome Xq12-q21.31 between AR (313700) and marker DXS1217 (maximum lod score of 4.42 at DXS1111 and DXS1197). The critical region spanned a 17-cM (25-Mb) interval. The authors noted the phenotypic similarities to Renpenning syndrome/MRXS8 (RENS1; 309500). Shrimpton et al. (2000) narrowed the critical region to an 11-cM (22-Mb) interval between DXS8040 and DXS1217, increasing the lod score to 4.75.