Incidence of Fragile X Syndrome in Korean Patients with Mental Retardation

Choi, Young Min; Hwang, Do Yeong; Jun, Jong Kwan; Choe, Jin; Park, Sung Hyo; Noh, Mee Kyung; Oh, Sun Kyung; Ku, Seung Yup; Suh, Chang Suk; Kim, Seok Hyun; Yang, Se Won; Cho, Soo Cheol; Moon, Shin Yong; Lee, Jin Yong

Abstract

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.