Duplication in chromosome 15q in a boy with the Prader-Willi syndrome; further cytogenetic confusion.

We describe a six-year-old boy with the typical features of Prader-Willi syndrome. Cytogenetic investigation revealed a chromosome aberration that has not been described yet, i.e. a duplication in the proximal half of 15q. Based upon banding-pattern the exact nature of the duplicated part could not be delineated. Both parents had a normal karyotype. Various hypotheses concerning the relationship between Prader-Willi syndrome and various chromosome 15 abnormalities are discussed.