Özet:

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 chro¬mosomal abnormalities of Turkish pediatric neurology outpatients. Materials and Methods: Cytogenetic and molecular screenings were performed to esti-mate the prevalence of the fragile X in 107 patients with mental retardation, language disorders, hyperactivity, develop¬mental 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.

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