AIM: To investigate the prevalence of fragile X syndrome(FXS) in intellectually disabled male and female Indonesians.METHODS: This research is an extension of a previously reported study on the identification of chromosomal aberrations in a large cohort of 527 Indonesians with intellectual disability(ID). In this previous study,87 patients had a chromosomal abnormality, five of whom expressed fragile sites on Xq27.3. Since FXS cannot always be identified by cytogenetic analysis, molecular testing of the fragile X mental retardation 1 CGG repeat was performed in 440 samples. The testing was also conducted in the five previously identified samples to confirm the abnormality. In total, a molecular study was conducted in 445 samples(162 females and 283 males).RESULTS: In the cohort of Indonesian ID population, the prevalence of FXS is 9/527(1.7%). The prevalence in males and females is 1.5%(5/329) and 2%(4/198), respectively. Segregation analysis in the families and X-inactivation studies were performed. We performed the first comprehensive genetic survey of a representative sample of male and female ID individuals from institutions and special schools in Indonesia. Our findings show that a comprehensive study of FXS can be performed in a developing country like Indonesia where diagnostic facilities are limited.CONCLUSION: The prevalence of FXS is equal in females and males in our study, which suggests that the prevalence of FXS in females could be underestimated. AIM: To investigate the prevalence of fragile X syndrome (FXS) in intellectually disabled male and female Indonesians. METHHODS: This research is an extension of a previously reported study on the identification of chromosomal aberrations in a large cohort of 527 Indonesians with intellectual disability ( ID). In this previous study, 87 patients had a chromosomal abnormality, five of whom expressed fragile sites on Xq27.3. Since FXS can not always be identified by cytogenetic analysis, molecular testing of the fragile X mental retardation 1 CGG repeat was performed in 440 samples. The testing was also conducted in the five previously identified samples to confirm the abnormality. In total, a molecular study was conducted in 445 samples (162 females and 283 males) .RESULTS: In the cohort of Indonesian ID population, the prevalence of the FXS is 9/527 (1.7%). The prevalence in males and females is 1.5% (5/329) and 2% (4/198), respectively. Segregation analysis in the families and X-inactivation studies We performed the first comprehensive genetic survey of a representative sample of male and female ID individuals from institutions and special schools in Indonesia. Our findings show that a comprehensive study of FXS can be performed in a developing country like Indonesia where diagnostic facilities are limited.CONCLUSION: The prevalence of FXS is equal in females and males in our study, which suggests that the prevalence of FXS in females could be underestimated.