ABSTRACT
In spite of tiny deletion of chromosomal segment in microdeletion diseases the affected individual represents severe clinical manifestation. The classical cytogenetic techniques including high resolution are unable to clarify the deleted segment. It is worthy performing FISH study for clinically suspected patients. The result of 39 blood samples and two amniotic fluid samples studied by FISH of peripheral blood [1-24 years old] and two amniotic fluid including: peripheral blood samples clinically suspected for Angelman syndrome, 15 cases for Prader-Willi syndrome and five children PB and two amniotic fluid for PWS/ AS syndrome are as follows: Seven samples of Angelman syndrome, three cases of Prader-Willi syndrome, and 2 cases of other samples totally, 12 of 40 [30%] were positive for deletion of critical segment 15 [q11-q13], confirming the clinical diagnosis. One blood sample for Angelman syndrome did not growth