The fragile X syndrome: the patients and their chromosomes.

We have reviewed recent publications, mostly from 1980 onwards, concerned with the problem of identifying patients with the fragile X chromosome and mental retardation, considering the two practical sides of the problem, that is, identification by their external appearance and by chromosomal studies. We conclude that this condition covers a large range of physical findings which occur in varying degrees in people with the chromosome marker. We have tried to clarify the existent criteria that have to be considered for an accurate cytogenetic diagnosis.