Neonatal diagnosis of Prader-Willi syndrome and its implications.

Although Prader-Willi syndrome (PWS) patients usually first present with neonatal hypotonia and feeding difficulty, they later show hyperphagia, obesity and mental retardation. Since deletions of chromosomes 15q11-q13 are noted in most PWS patients cytogenetic analysis allows one to diagnose infants suspected of PWS with a greater certainty. We report on 5 hypotonic infants clinically suspected of PWS in the first 3 months of life, whose diagnosis was confirmed by cytogenetic studies showing monosomy of 15q11-q13. Early diagnosis of PWS can lead to prevention of obesity, but counseling of parents has been difficult. Although there are significant benefits to the early diagnosis of PWS, the cost-effectiveness and practicality of screening all hypotonic infants using high resolution cytogenetic analysis has been addressed systematically.