Cytogenetic and Molecular Investigation in Children with Possible Fragile X Syndrome

Objective: Fragile X syndrome (FXS) is the most common cause of inherited mental retardation and is due to a mutation in the X-linked FMR1 gene. Molecular genetic testing and chromosome analysis are indicated for this disorder. In this context, we tried to determine the frequency of the FXS, and other chromosomal abnormalities of Turkish pediatric neurology outpatients. Materials and Methods: Cytogenetic and molecular screenings were performed to estimate the prevalence of the fragile X in 107 patients with mental retardation, language disorders, hyperactivity, developmental delay or fragile X syndrome phenotype. Only 26 out of 107 patients were screened, molecularly. Results: Cytogenetically fragile X-positive cells was found in 8 cases (7.5%) of 107 patients; in 4.7% of males and in 2.8% of females. The autosomal fragile sites (FS) was found in 14 (13.1%) cases. One (0.9%) patient had pericentric inversion of chromosome 9. Molecular analysis were performed for 26 patients and all patients showed normal CGG expansion. Conclusion: In diagnosis of fragile X syndrome, chromosome analysis must be run in conjunction with the molecular studies. It is recommended that all members of the fragile X family under risk should be screened both by cytogenetic and molecular methods. Genetic counseling can be useful to patients and families considering genetic testing.