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Subcutaneous fat necrosis of the newborn
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Subcutaneous fat necrosis of the newborn (SCFNN) is an uncommon, self-limiting panniculitis that affects term or postterm infants in the first weeks of life. It is characterized by firm subcutaneous nodules and plaques over areas of fat distribution, predominantly the cheeks, trunk, buttocks, and proximal extremities. These may be flesh-colored, erythematous, or blue. Lesions vary in size from just a few millimeters to large coalescent plaques and can become calcified or fluctuant with liquefied fat. SCFNN generally follows a benign course and resolves spontaneously without residua over weeks to months, though atrophy of the skin or small pitted scars may develop.
The exact etiology of SCFNN is unknown. It is strongly associated with perinatal stress and as such is more common in infants delivered via caesarean section or who experienced birth trauma. Therapeutic hypothermia, which involves whole-body cooling of neonates to reduce the neurologic sequelae associated with birth asphyxia or improve outcomes during cardiac surgery, is a common iatrogenic cause.
The most serious complication of SCFNN is hypercalcemia, which occurs in up to half of patients. Detectable hypercalcemia usually occurs within 30–60 days following onset, as panniculitic lesions are resolving, but can occasionally precede the development of SCFNN.
Hypercalcemic infants may present with lethargy, irritability, hypotonia, poor feeding, vomiting, dehydration, constipation, polyuria, or failure to thrive. Seizures, renal failure, or cardiac arrest are the most serious sequelae. Persistent hypercalcemia can result in nephrolithiasis, or metastatic calcification in the brain, heart, skin, or gastric mucosa. Less common complications of SCFNN include thrombocytopenia, hypoglycemia, hypervitaminosis D, and hyperlipidemia.
Management Strategy
A clinical diagnosis can usually be made without the need for biopsy. Fine-needle aspiration of the subcutaneous lesions can be done if there is diagnostic uncertainty. Typical histology shows a dense mononuclear cell infiltrate within the subcutaneous fat with needle-shaped clefts within adipocytes, and fat necrosis. Imaging is not required for diagnosis, though IT may help exclude other differential diagnoses. Total serum and ionized calcium should be measured at diagnosis, and again at 30, 45, and 60 days, or in any infant showing signs of hypercalcemia within 6 months of diagnosis. Parents should be counseled about symptoms of hypercalcemia and advised to attend a physician should their child develop these symptoms.
Children with mild hypercalcemia should have calcium levels checked weekly for 4 weeks, or until resolution of hypercalcemia. A renal ultrasound should be done in any infant who develops hypertension and considered in those with moderately or persistently elevated serum calcium.
Specific Investigations
Subcutaneous fat necrosis after moderate therapeutic hypothermia in neonates
Strohm B, Hobson A, Brocklehurst PA, et al. Pediatrics 2011; 128: e450–2.
The UK Total Body Hypothermia registry records patients who have therapeutic cooling for hypoxic ischemic encephalopathy. Over a 4-year period 12 patients developed SCFNN from 1239 cases registered (≈1%).
The incidence of SCFNN in neonates who have therapeutic hypothermia ranges from 1% to 3%. Skin examination should be done regularly following treatment and parents should be advised of signs of SCFNN and hypercalcemia on discharge.
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