Problems in the diagnosis of fragile X syndrome in young children are still present.

Fragile X syndrome is common; its prevalence approaches 1 per 5,000. Fragile X syndrome is the most common inherited cause of mental retardation. Many professionals must deal with fragile X individuals on a daily basis. However, despite the diverse information on the epidemiology, clinical features, unique pattern of inheritance, cytogenetic, and molecular diagnosis and scales for the diagnosis of this syndrome, the diagnosis of fragile X syndrome is still not always made by the patients' specialists. Here we present the difficulties in the diagnosis of fragile X syndrome in 11 children under 8 years of age, 10 boys and one girl. We report data on initial symptoms, behavioral features, and physical and mental development before molecular studies were considered. The possible causes for the diagnosis delay were multiple: nonspecific features (e.g., macrocephaly, overgrowth, obesity), unremarkable physical examination, family history apparently noncontributory, and lack of or delayed molecular testing. Careful clinical examination of young children and DNA screening in case of doubt, and education of professionals in medical specialty areas, behavioral sciences, education, and other fields are recommended. Copyright 2001 Wiley-Liss, Inc.