Summary Prader-Willi Syndrome is a congenital condition caused by a partial chromosome 15 deletion that presents with obesity, failure to thrive, mental retardation, hip dysplasia, and scoliosis. Diagnosis is made with physical examination at birth and genetic testing to identify a missing portion of chromosome 15. Treatment involves a multidisciplinary approach to address orthopedic manifestations, cognitive abnormalities, and metabolic abnormalities. Epidemiology Incidence 1 in 25,000 births Etiology Genetics partial chromosome 15 deletion Associated conditions orthopaedic growth retardation hip dysplasia juvenile onset scoliosis genu valgum pes planus leg length difference medical hypotonic obese intellectually impaired insatiable appetite hypoplastic genitalia Presentation Symptoms failure to thrive in infancy weak cry aggressive behavior abnormal facial features almond-shaped eyes small, down-turned mouth Physical exam small for gestational age hypoplastic or undescended testicles delayed onset of puberty truncal obesity at 1-4 years of age slow motor development may show signs of right-sided heart failure knee and hip instability Imaging Radiographs recommended views scoliosis films consider AP pelvis to identify hip dysplasia Evaluation Diagnosis is based primarily on physical exam at infancy Labs glucose intolerance high insulin level failure to respond to LHrF high CO2, low O2 Genetic testing may identify missing portion of chromosome 15 to confirm diagnosis Treatment Nonoperative bracing indications: curves over 20°-25° in children less than 10 years of age efficacy may be compromised by obesity Operative growth rods indications children under the age of 10 who cannot maintain a curve under 50° posterior spinal fusion indications- older children with curves greater than 50° complications may be higher than in idiopathic scoliosis