Prader-Willi syndrome and chromosomal mosaicism 46,XY/47,XY,+mar in two cases.

Two cases of the Prader-Willi syndrome with 46,XY/47,XY,+mar are reported. The majority of Prader-Willi patients with chromosome abnormalities have either 15/15 translocations or mosaicism. Both of these aberrations presumably occur after fertilization. A possible relationship between high parental age and chromosome abnormalities in the Prader-Willi syndrome is discussed.