Sir.—The fragile X-positive form of the Martin-Bell syndrome is a wellrecognized cause of X-linked mental retardation. In addition to mental retardation and the fragile X chromosome, the condition is characterized by macrocephaly, large or prominent ears, relatively long and narrow face, prominent mandible, high-arched palate, macro-orchidism, verbal disability, and behavioral disturbances.1 The diagnosis is usually made by demonstrating the fragile X chromosome in individuals with a family history suggesting X-linked mental retardation, by screening for the aforementioned physical and chromosomal abnormalities in mentally retarded males, or by detecting the fragile X as an incidental cytogenetic finding.2,3 Here we report the sporadic occurrence of the Martin-Bell syndrome in a 6-year-old, normalappearing boy with severe retardation, and we wish to stress the importance of routinely screening retarded individuals for this condition.
Report of a Case.—The pregnancy, labor, and delivery of the child were uncomplicated. His development had always