Mental Retardation, X-Linked, Syndromic 12

Clinical Features

Wilson et al. (1992) described an apparently 'new' type of nonspecific X-linked mental retardation in 3 generations of a family. Three affected males had severe mental retardation (IQ 20-30), mutism, growth failure, frequent infections, seizures, and the following minor anomalies: brachycephaly, frontal hair whorl, square face, large mouth, thick lips, and prognathism. Comparison of these patients with a large number of X-linked types of mental retardation, including many that might be classified as 'nonspecific,' showed no entirely comparable phenotype. The absent or delayed speech was particularly striking. For example, the oldest patient, aged 27 years, had aphasia despite an interactive personality and considerable facility with sign language. Hearing was normal.

Mapping

By linkage analysis using probes for DXS255 located at Xp11.22 in a family segregating a syndromic form of mental retardation, Wilson et al. (1992) obtained a maximum 2-point lod score of 2.10 if phase was inferred and 1.20 if it was not. Crossovers were shown with probes mapping to regions Xp22, Xp21, and Xq28.