Life-threatening condition occurring in preterm neonates and debilitated full-term neonates, characterized by hardening of the skin and subcutaneous adipose tissue. Onset is usually within the first days to weeks after birth. Typically affects the buttocks, thighs, and trunk, although it can spread to almost any part of the body (spares the palms, soles, and genitalia). The skin becomes waxy, cool, and mottled and cannot be pinched into a fold. Results in restricted breathing, poor feeding, dehydration, hindered movement, joint contractures, and failure to thrive. Although etiology is uncertain, associations include hypoglycemia, sepsis, shock, hypothermia, metabolic abnormalities, and other serious underlying illnesses. Prognosis is poor.