Korean J Obstet Gynecol.  1999 Nov;42(11):2458-2464.

Incidence of Fragile X Syndrome in Korean Patients with Mental Retardation


Fragile X syndrome is the most common cause of inherited mental retardation. It accounts for 0.2% - 2.7% of patients with mental retardation, based upon the molecular genetic diagnosis. However, the exact prevalence of fragile X syndrome in Korean patients with mental retardation is unknown. We have performed cytogenetic and molecular analysis for fragile X syndrome in 212 Korean patients with mental retardation. Among them, six patients (2.8%) was identified as carrying fragile X syndrome by both cytogenetic and molecular analysis. The results by cytogenetic analysis was identical to those by molecular analysis. Cytogenetic analysis of 6 carriers (mothers of patients with proven fragile X syndrome) showed a fragile X chromosome in one patients (16.7%) while molecular analysis revealed premutation in all patients. PCR method using Klentaq1 Pfu polymerase showed the same results as those by PCR method using Exo(-) Pfu polymerase, but the former method is recommended because of its simplicity in technical aspect. These data suggest that the prevalence of fragile X syndrome in Korean patients with mental retardation is 2.8%, not significantly different from those in Caucasians.


Fragile X syndrome; Mental Retardation; Southern blot analysis; PCR; Chromosome analysis; Southern

MeSH Terms

Cytogenetic Analysis
Fragile X Syndrome*
Intellectual Disability*
Molecular Biology
Polymerase Chain Reaction
X Chromosome
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