Deletions of Chromosome 15 as a Cause of the Prader–Willi Syndrome

THE Prader–Willi syndrome consists of muscular hypotonia, obesity, short stature, small hands and feet, hypogonadism, and mental retardation. Although an autosomal-recessive mode of inheritance has been suggested, the origin of the disease has been problematic. In 1976 Hawkey and Smithies described a patient with the syndrome and an abnormal karyotype showing a 15; 15 Robertsonian translocation.1 Noting similar translocations involving at least one D-group chromosome (numbers 13–15) in earlier reports on the syndrome, they suggested that loss of the short arm of chromosome 15 because of unbalanced translocation might be a specific cause of this syndrome. Since their report, seven . . .