A syndrome characterized at birth by the lack of spontaneous movements and protective reflexes, thus giving an appearance of severe brain damage. Profound hypotonia may cause asphyxia. Sucking and swallowing reflexes are absent or decreased. Deficient thermoregulation, amyotonia, and hypogonadism are usually associated. After a few weeks or months, the affected infants become more responsive and more alert. Areflexia disappears gradually but hypotonia may persist longer. This phase is marked mainly by mental subnormality, delayed growth and motor development, speech defect, lack of emotional control, voracious appetite leading to obesity, hypotonia, hyperlaxity, delayed bone maturation, and multiple orofacial and other disoders. There is a tendency to develop diabetes mellitus and cardiac failure in some patients. Pain insensitivity is common. Prader-Willi habitus associated with osteopenia and camptodactyly is known as the Urban-Rogers-Meyer syndrome.