Deletion of chromosome 15pter-->q11.2 due to t(Y;15) in a boy with Prader-Willi syndrome.

Chromosome analysis of lymphocytes from a patient with the clinical presentation of Prader-Willi syndrome showed the presence of 45 chromosomes, including a der(Y) resulting from an unbalanced t(Y;15)(q12;q11.2). In situ hybridization using DYZ3 and DYZ2 showed positive signals at the paracentromeric region on the short arm and at the heterochromatic region of the long arm of the Y chromosome, respectively. The Prader-Willi syndrome in this patient is caused by the deficiency of a very small region involving 15cen-->q11.2.