The classic description of sclerema neonatorum (SN) is credited to Underwood, who described it in 1784 and appropriately termed it "skinbound disease." In 1817, Alibert introduced the term sclerema, derived from the Greek word skleros, meaning hard. Sclerema neonatorum is a disorder of the subcutaneous fat in debilitated neonates and is considered best as a sign of a potentially fatal underlying disease process and not a specific disease entity.  A thorough review of the nomenclature, clinical findings, histological features, differential diagnosis, and management of sclerema neonatorum was published in 2008. 
The Medscape Pediatric Dermatology Resource Center may be of interest.
In an infant, fat has a higher saturated-to-unsaturated fatty acid ratio compared to adult fat and thus, a higher melting point. Prematurity, hypothermia, shock, and metabolic abnormalities have been postulated to further increase this ratio, possibly as a result of enzymatic alteration allowing precipitation of fatty acid crystals within the lipocytes. This condition has been suggested to result in the dramatic clinical findings in affected skin. X-ray diffraction techniques have confirmed that infants with sclerema neonatorum have an increase in saturated fats and that the crystals within the fat cells are composed of triglycerides. [3, 4]
The exact incidence of sclerema neonatorum is unknown. All studies describe sclerema neonatorum as extremely rare. The number of reported cases in recent years has declined, probably as a result of better neonatal care.
A 10% incidence of sclerema neonatorum was documented in preterm neonates admitted to a hospital in Bangladesh. Risk factors for developing sclerema neonatorum in these infants included poor feeding, jaundice, and bacteremia. 
No racial predilection has been reported.
Sclerema neonatorum shows a slight male predominance, with an estimated male-to-female ratio of 1.5:1. 
Sclerema neonatorum is a disease confined to the newborn period. Sclerema neonatorum can present at birth, but onset within the first week of life is more common. The oldest reported infant presented with Pseudomonas septicemia at age 106 days.
Because sclerema neonatorum invariably is associated with serious underlying disease, the mortality rate is high. In different series, the reported mortality rates range from 67-88%, with death occurring hours to days after onset. If the underlying disease is treated successfully, the skin softens and returns to normal.
One case of an infant with consecutive episodes of sclerema was reported to occur in a severely ill infant, and both episodes resolved after appropriate treatment of underlying illness.