A Case of Prader-Willi Syndrome with an Unusually Large 15q Deletion Due to an Unbalanced Translocation to Chromosome 2 45,XX,-15, der(2) t(2;15)(q37:q13)

ABSTRACT

Prader-Willi syndrome is a disease of chromosome 15, which is characterized by severe hypotonia and feeding difficulty in neonates, followed by development of obesity, mental retardation, and hypogonadism. Approximately 70% of the patients have a paternal deletion on chromosome 15q11-13, which is mainly a microdeletion, and a large deletion due to an unbalanced structural translocation of the proximal long arm of chromosome 15 to several other chromosomes is rarely found. We encountered a neonatal case with Prader-Willi syndrome who had sustained hypotonia and feeding difficulty. On high-resolution chromosome analysis, deletion of the short arm and the proximal part of the long arm of chromosome 15, with unbalanced translocation of the remaining part of chromosome 15(q13-qter) to the terminal part q37 of chromosome 2, was shown to be . Through FISH (Fluorescence in situ hybridization) and methylation-specific DNA PCR, we confirmed the deleted q11-13 was derived from the father.