The heterozygous deletion of the SNRPN, TUBGCP5, UBE3A, MKRN3, GABRB3, ATP10A, MAGEL2, NDN, and NIPA genes in the Prader-Willi syndrome (PWS)/AS-related regions of chromosome 15q11 was analyzed by MLPA from the genetic DNAs extracted from the blood sample of the patient and the patient's parents. Here, NDN is linked to Prader-Willi syndrome.