A CLINICAL, CYTOGENETIC AND MOLECULAR STU DY OF 10 PATIENTS WITH THE PRADER-WILLI-SYNDROME

BACKGROUND: The Prader-Willi syndrome (PWS) is a neurogenetic disorder associated with abnormalities in the chromosomal region 15q11-13 of p aternal origin. Most cases (65-85%) have a deletion involving the pate rnally derived chromosome and the remainder (20-25%) have a maternal u niparental disomy. Some patients have a defect in the imprinting proce ss. We report the results of molecular, cytogenetic and clinical studi es on 10 PWS patients. PATIENTS AND METHODS: 18 suspected PWS patients were classified as PWS typical or not typical as they fulfilled or no t the clinical criteria for PWS. Cytogenetic studies-high resolution c hromosome banding analyses (HRGTG) and fluorescence in situ hibridizat ion (FISH) -and molecular genetic analyses- microsatellite markers and Southern blotting- were carried out from peripheral blood lymphocytes . RESULTS: PWS was confirmed in 10 probands, 8 fulfilled the clinical criteria for PWS and showed cytogenetic and/or molecular abnormalities , In 2 patients without clinical or cytogenetic data, diagnosis was co nfirmed by molecular methods only. Cytogenetic and molecular findings describe a characteristic clinical picture of PWS. CONCLUSIONS: Cytoge netic techniques (FISH and HRGTG) confirmed PWS diagnosis in 40% of ca ses, microsatellite studies in 70% of them and Southern blotting (the metilation test) in 100% of cases. Southern blotting is the method of choice for rapid diagnostic testing of patients suspected of having PW S.