X linked mental retardation: a family with a separate syndrome?

Four males with X linked mental retardation are described. Manifestations similar to those seen in the FG syndrome include severe constipation, tall, broad foreheads, hypotonia, and cowlicks of the hair line, but no individual patient had all the features of the syndrome and none had macrocephaly. The facial appearance was distinctive but different from that seen in the FG syndrome. The cases are presented in order to discuss the phenotypic limits of the FG syndrome and to consider the need to separate other distinct but similar entities.