Prader-Willi syndrome, first described in 1956, occurs in approximately 1 in 25,000 live births.^[118,119]The major clinical manifestations include infantile hypotonia; feeding problems; failure to thrive; rapid weight gain occurring between ages 1 and 6 years; a characteristic dysmorphic facial appearance with a narrow bitemporal diameter, almond-shaped eyes, palpebral fissures, down-turned mouth; developmental delay and mental retardation. Hypogonadism may be present at birth, with cryptorchidism, scrotal hypoplasia, and a small penis in boys; poor development of the labia minora and clitoris in girls; and delayed onset of puberty associated with low sex steroid hormones, low gonadotropins, and blunting of the gonadotropin response to GnRH. In addition, these patients have short stature (associated with growth hormone deficiency) and behavioral problems that appear during childhood and are characterized by temper tantrums, aggressive …