A step-wise diagnosis of fragile X syndrome in Taiwan

Fragile X syndrome (FXS), an X-linked dominant disorder, is one of the common forms of inherited mental retardation. This project aimed at identifying fragile X syndrome patients in schools by a two-step diagnosis with questionnaire and photography followed by molecular analysis. A total of 734 children with mental retardation were enrolled from kindergartens, primary schools, junior high schools, and schools for the mentally retarded. School teachers or nurses administered the questionnaires and took pictures of the faces and hands for of the patients. After viewing of the questionnaire and photos by a geneticist, 145 cases were selected for molecular study and 11 cases were identified as having full mutations in the FMRI gene. The detection rate was 1.5% (11 in 734) in all enrolled cases, and was 7.6% (11 in 145) in those who underwent molecular test. Those affected by FXS were more likely to have simian crease (p<0.001) and a head circumference larger than the 50th percentile (p=0.0295), and those who were not affected by FXS were lower in gestational age (p=0.0243). This screening method is useful for the detection of fragile X syndrome.