OBJECTIVETo definite the etiopathogenisis by carrying out the genome-wide copy number variation analysis for a suspect patient with Prader-Willi syndrome.

METHODSThe peripheral blood was collected from the patient who was diagnosed as having Prader-Willi syndrome, as well as his parents for conventional cytogenetic G-banding and high resolution chromosome assay. Genomic DNA of the child patient was extracted from the blood to perform the genome-wide copy number variation analysis.

RESULTSThere was a heterozygosis deletion of a 5Mb region in chromosome 15q11.2-q13.1 by the genome-wide copy number variation analysis, but no abnormality was observed in high resolution chromosome assay in the child patient and his parents. Baylay and Gesell developmental scale was assessed regularly; the results suggested that the IQ of the child patient was 60-70, according with the clinical feature of Prader-Willi syndrome.

CONCLUSIONThe heterozygosis deletion in chromosome 15q11.2-q13.1 is the cause of Prader-Willi syndrome in this family. Further molecular genetics detection can make up for the insufficiency in cytogenetics methods, when no abnormality is observed at the level of cytogenetics in patients with Prader-Willi syndrome.