Pathophysiology:
(1) The skin of a newborn may take on a reticulate or marble appearance when there is arteriolar vasoconstriction and increased blood viscosity.
(2) Infants normally have a higher ratio of saturated to unsaturated fatty acids in their adipose tissue, which resists solidification. If adipose cell enzymes are immature or inactivated due to acute illness, then the ratio may change, resulting in crystallization at a lower temperature.
(3) Crystallization of fatty acids is associated with breakdown of lipocytes which incites an inflammatory reaction.
Risk factors:
(1) perinatal asphyxia
(2) birth trauma
(3) aspiration of meconium
(4) neonatal hypoxemia
(5) sepsis or other infection
(6) hypothermia or cold injury (including therapeutic hypothermia)
Clinical findings:
(1) red to violaceous plaques and nodules appear over the cheeks, back, arms, buttocks and/or thighs within a few days of delivery
(2) affected infants are usually full term or post-term (premature infants may have little subcutaneous fat)
(3) infants may be ill, with hypoglycemia, anemia, thrombocytopenia, and/or hypercalcemia. Hypercalcemia may be a significant finding in more severely affected infants.
(4) the lesions are self-limited and resolve within a few weeks if the child survives and as adipose tissue deposits develop
(5) biopsy shows fat necrosis and fat crystals, with or without a granulomatous response
