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Genetic diagnosis of Prader–Willi syndrome

Khedr, Azzah A.; Meguid, Nagwa A.; Mohamed, Amal M.; Ismail, Suzan R.; Nazmy, Nahla A.; Hassan, Heba A.; Essawi, Mona L.

Middle East Journal of Medical Genetics: July 2016 - Volume 5 - Issue 2 - p 45–53
doi: 10.1097/01.MXE.0000484369.78928.9e
Original articles

Introduction Prader–Willi syndrome (PWS) is a rare genetically determined congenital neurodevelopmental disorder due to loss of paternally active genes on a critical region on chromosome 15(q11–q13).

Aim This study aimed at confirming/excluding PWS in clinically suspected patients through feasible laboratory techniques on the cytogenetic level, cytomolecular level using fluorescent in-situ hybridization (FISH) technique, and DNA level through methylation tests, which are greatly important for phenotype/genotype correlation, early diagnosis, and proper counseling.

Materials and methods Combined cytogenetic, FISH, and methylation studies were conducted on 23 patients who were clinically suspected as having PWS.

Results Of 23 patients subjected to cytogenetic study of metaphase spreads, 10 patients had suspected deletion of 15q11–q13. FISH confirmed the deletion in six patients, with mosaicism in one patient, and detected deletion in four patients with normal karyotype using metaphase spread. Molecular methylation studies were conducted on 17 patients; 11 cases were found to be PWS.

Conclusion We reinforce the necessity of analysis of DNA methylation within the chromosome 15q (11–13) region. DNA methylation analysis can detect patients with PWS either due to microdeletions or mutations.

Departments of aHuman Cytogenetics

bSpecial Needs

cMedical Molecular Genetics, National Research Centre, Cairo

dDepartment Human Cytogenetic, Medical Research Institute, Alexandria University, Alexandria, Egypt

Correspondence to Azzah A. Khedr, MSc, Department of Human Cytogenetics, National Research Centre, El-Bohouth Street, Dokki, Cairo 12311, Egypt Tel: +20 100 171 3048; fax: +20 228 412 239; e-mails: and

Received January 23, 2016

Accepted March 23, 2016

© 2016 Middle East Journal of Medical Genetics
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