A Study of Prader-Willi Syndrome and Angelman Syndrome with the Deletion of Same Loci in 15 Chromosome

Kim, Deok Soo; Shin, Young Lim; Ko, Tae Sung; Seo, Eul Ju; Yoo, Han Wook

Abstract

PURPOSE: In general, genetic disorders have the numerical or structural abnormalities of chromosome. There are clinically two different disorders, Prader-Willi syndrome(PWS) and Angelman syndrome(AS), which have the deletion of specific region of 15 chromosome originated from father or mother by genetic imprinting phenomenon. We reported the results of genetic study including DNA methylation analysis and fluorescence in situ hybridization(FISH), in addition to clinical findings.
METHODS
We studied 20 patients of PWS and AS diagnosed in pediatric department of Asan Medical Center from 1992 Feb. to 2001 Apr., retrospectively. We analyzed the clinical manifestations of the disorders and performed cytogenetic studies from the peripheral blood. And we the methylation pattern and FISH, using the probe for single nucleotide ribonucleoprotein N(SNRPN) locus within the Prader-Willi/Angelman region (15q11-q13).
RESULTS
Among 16 patients of PWS, the age at initial visit was from 3 days to 12 years and the male to female ratio was 1.67:1. Seven patients had the history of intrauterine growth retardation or fetal distress. The chief complaints at initial presentation were classified on age. Under 3 years(n=10), there were hypotonia(4), development delay (3), feeding difficulties(2), and tachycardia(1). Above 3 years(n=6), we found short stature(2), respiratory difficulty(1), seizure(1), obesity(1), and undescended testes(1). DNA methylation study showed the methylation of 15 chromosome originated from paternal chromosome and the microdeletion by FISH was detected in all 12 among 12 patients (100%). In AS(n=4), the sex ratio(M:F) was 3:1 and age at presentation was from 15 months to 6 years. The important sign was severe developmental delay in all patients, combined with mental retardation in one case. Other clinical manifestations were depigmentation of skin and hair(4), prognathism(3), seizure(3), frequent laughing(2), undescended testes(1), hypotonia(1), and hyperactivity(1). FISH study was performed and showed the microdeletion of 15 chromosome in all 4 patients.
CONCLUSION
We studied the clinically two different disorders, PWS and AS, with the deletion of same region of 15 chromosome and reported the results of the clinical and genetic analysis based on clinical findings and DNA analysis and FISH study, respectively.