Phenotypic checklist to screen for fragile X syndrome in people with mental retardation

The development of a phenotypic checklist for identifying people with fragi le X syndrome is described. The checklist was designed to identify people w ith developmental disabilities of unknown causes for molecular genetic test ing for fragile X syndrome. The list consists of 28 items (7 on physical ch aracteristics and 21 on behavioral features). Validation data were collecte d for 110 boys and men with fragile X syndrome and for 79 members of a cont rol group, matched for CA, level of cognitive development, and social (mal) adaptation. On the basis of checklist results, those boys who are likely to be diagnosed as having fragile X syndrome can be identified. The screening list can be considered to be a consistent, reliable, and valid instrument.