Gene for nonspecific X-linked mental retardation (MRX 47) is located in Xq22.3-q24

We describe a large family with nonspecific X-linked mental retardation (MRX 47). An X-linked recessive transmission is suggested by the inheritance from the mothers in two generations of a moderate to severe form of mental retardation in six males, without any specific clinical findings. Two point linkage analysis demonstrated significant linkage between the disorder and two markers in Xq23 (Zmax = 3.75, θ = 0). Multipoint linkage analyses confirmed the significant linkage with a maximum lod score (Z = 3.96, θ = 0) at DXS1059. Recombination events observed with the flanking markers DXS1105 and DXS8067 delineate a 17cM interval. This interval overlaps with several loci of XLMR disorders previously localized in Xq23–q24, which are reviewed herein. Am. J. Med. Genet. 72:324–328, 1997. © 1997 Wiley-Liss, Inc.