Objective: The fragile X syndrome, a common cause of mental retardation, is poorly recognized even in families at risk. The aims of our study were to evaluate the possibility of finding previously unidentified carriers of the genetic defect in fragile X families, to use this information in antenatal diagnosis, and to study the attitudes of these families to genetic screening.
Study design: We identified 59 fragile X families living in a population of 900,000 inhabitants. A deoxyribonucleic acid test on the FMR1 gene was offered to 1071 persons in these families who had a risk of at least 12.5% of having the fragile X premutation or full mutation.
Results: A total of 48.1% of the persons who were offered the test accepted it. A diagnosis was made in 20 male and 66 female subjects with the full mutation and in 30 male and 133 female subjects with a premutation. All 21 pregnant carriers of this mutation accepted chorionic villus biopsy.
Conclusion: Pregnant relatives should be informed of the availability of screening for fragile X carrier status in families with a member having clinical fragile X syndrome. Antenatal clinics offer a good gateway for approaching families with this inherited developmental defect.