RESUMEN
PURPOSE: Two different disorders, Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are caused by the deletion of 15q11-13 or the maternal/paternal uniparental disomy of chromosome 15 (mUPD(15)/pUPD(15)) through the genomic imprinting phenomenon. We studied the clinical manifestations of both diseases and genotype-phenotype correlations in PWS. METHODS: We retrospectively analyzed medical records of patients who had been genetically confirmed as PWS or AS from December 1998 to March 2010 at Asan Medical Center. Clinical characteristics at diagnosis and genetic causes were reviewed. In PWS, clinical characteristics of the patients with microdeletions were compared with those with mUPD(15). RESULTS: During the study period, we found 90 patients with PWS and 30 with AS. In cases of PWS, the male to female ratio was 1.65:1 and the mean age at initial diagnosis was 41 months. Symptoms at first diagnosis were hypotonia (70 cases) and developmental delay (66 cases). More hypopigmentation and eye abnormalities occurred in the microdeletion group (n=62) than in the mUPD(15) group (n=21). In AS, the male to female ratio was 1.3:1 and the mean age at initial diagnosis was 23 months. Distinguishing symptoms were speech impairment, seizure, and behavioral uniqueness. Microdeletion by FISH was detected in 19 patients among 20 patients and one of the non-deletion patient showed pUPD(15) on a DNA methylation test. CONCLUSION: PWS and AS, two distinct neurogenetic disorders with different clinical presentations were the first known examples of human diseases involving imprinted genes. This study about clinical characteristics and genetic analysis of PWS and AS may help our understanding of these diseases and thus, assist in making correct diagnoses.