Familial X-linked mental retardation and isolated growth hormone deficiency: clinical and molecular findings.

We report on several members of a family with varying degrees of X-linked mental retardation (XLMR), isolated growth hormone deficiency (IGHD), and infantile behaviour but without other consistent phenotypic abnormalities. Male patients continued to grow until well into their twenties and reached a height ranging from 135 to 159 cm. Except one, all female carriers were mentally normal; their adult height ranged from 159 to 168 cm. By linkage studies we have assigned the underlying genetic defect to the Xq24-q27.3 region, with a maximum lod score of Z = 3.26 at theta = 0.0 for the DXS294 locus. The XLMR-IGHD phenotype in these patients may be due to pleiotropic effects of a single gene or it may represent a contiguous gene syndrome.