Schaaf-Yang syndrome has clinical features similar to Prader-Willi syndrome including neonatal hypotonia with failure to thrive which transitions into excessive eating and subsequent obesity. Developmental delays and intellectual disabilities are common, and some patients exhibit autistic features. Physical characteristics include hypogonadism, short stature, small hands, almond shaped eyes, and coarse features. Seizures occur in some patients. Schaaf-Yang syndrome appears to be caused by de novo mutations in MAGEL2.