Prevalence and clinical characteristics of fragile X syndrome at child development clinic, Ramathibodi Hospital.

Fragile X syndrome, the most common cause of inherited mental retardation, is an X-linked genetic disorder caused by an expanded CGG repeat in the fragile X mental retardation 1 gene. It is characterized by mental retardation, behavioral features, and physical features, such as a long face with large protruding ears and macro-orchidism. A screening for the syndrome was conducted in a representative sample of pediatric patients, who had developmental delay or mental retardation with unknown cause, at the Child Development Clinic, Ramathibodi Hospital. The DNA test was performed on all patients using PCR and southern blot techniques. Five positive cases were detected from 114 screened subjects, and more four cases confirmed among other family members. Two of five positive families initially denied a family history of mental retardation. Among 9 cases of fragile X syndrome, four had hyperactivity and two had autistic like behavior. More than half had rather a long face or prominent ears. Three boys had macro-orchidism.

A clinical checklist for fragile X syndrome: screening of Thai boys with developmental delay of unknown cause.

The aim of this study was to determine a cost-effective clinical checklist for fragile X syndrome (FXS) screening in a Thai male pediatric population with developmental delay of unknown cause. We studied 179 non-FXS male patients and 27 FXS patients from 18 families (age < or = 15 years). A six-item clinical checklist was used including family history (FH), long and narrow face (F), prominent and large ears (E), attention deficit/hyperactivity (AH), autistic-like behavior (AT) and testicular volume (T). These were scored as 0 if absent, 1 if borderline, and 2 if present. All patients were tested by using PCR and/or southern blot for the FMR1 gene. We used a logistic regression model from a computer program to analyze the data (Stata, version 5.0). We used logistic regression with cluster in the same family (average score) to eliminate bias from the related FXS cases. We found that a five-item checklist, 2FH + F + 0.5E + 2AH + T = total score, was the best model. When we used this clinical checklist with a threshold of total score of 4, 78.7 per cent of the screened cases with total scores < or = 4 could be eliminated as negative cases. In addition, all positive FXS cases had total scores > 4. We propose this five-item model for FXS screening in clinical pediatric practice, particularly from Asian population settings.