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.

Chromosome 22q11 deletion syndrome: the first three cases reported in Thailand.

The DiGeorge, velocardiofacial, and conotruncal anomaly face syndromes were originally described as separate disorders due to different concerns regarding phenotypes. However, all these disorders have some common clinical manifestations, including congenital heart defect, facial anomaly, and developmental delay. It is now clear that most cases of these syndromes have a common cause resulting from microdeletion of chromosome 22q11. This study reports the first three cases of Thai children presented with developmental delays. All are females who were known cases of congenital heart diseases. Their minor facial anomalies were subtle and not previously recognized as of any syndromes. The chromosome study by fluorescent in situ hybridization technique yielded microdeletion of chromosome 22q11. Without known prevalence in Asian populations, except in Japanese children, further study for chromosome 22q11 deletion syndrome in Asian children with conotruncal heart defects, who also have minor facial anomalies or developmental delays, should be undertaken.