Prader-Willi syndrome (PWS), a neuroendocrine disorder could be due to: a large paternally derived chromosome deletion of 15q11-13, to maternal uniparental disomy (UPD), or imprinting mutation (IC); amongst this last group five families, with inherited microdeletion encompassing SNRPN were described; in these families excluded a typical large deletion. Families with more than a child with PWS by classic large deletion have not been published.