Screening of Prader-Willi syndrome and Angelman syndrome in school children with moderate to profound mental retardation in Southern Taiwan

Background and Purpose: Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are caused by deficiencies of gene expression from paternal or maternal chromosome 15q11-q13, respectively. The study was conducted to estimate the prevalence of PWS and AS in children with moderate to profound mental retardation in Taiwan. Methods: The screening began with methylation studies in all enrolled cases. If methylation results were positive, Fluorescence in situ hybridization (FISH) and polymerase chain reaction (PCR) was used to determine whether deletion, uniparental disomy, or imprinting mutation was present. Results: Of 1053 children with moderate to profound mental retardation, we identified three cases of AS (0.28%) and one case of PWS (0.09%). Conclusions: The prevalence of PWS is lower than AS in school children with moderate to profound mental retardation. The greater number of AS identified than that of PWS is most likely a reflection of more severe mental retardation for AS than for PWS.