Prader-Willi syndrome (PWS) is a rare genetic disorder with an estimated incidence of 1 in 21,000 caused by the loss of function of specific genes on the paternal chromosome 15 (15q11-q13 region). It affects multiple systems and is characterized by distinctive dysmorphic features along with a set of clinical features that evolve over time. The phenotype was first described in 1956,1 and over time, the clinical spectrum has been delineated.2