SUBCUTANEOUS FAT NECROSIS OF THE NEWBORN
Subcutaneous fat necrosis of the newborn (SCFN) is a panniculitis which typically affects term and post-term newborns, often in cases of pregnancy complication or perinatal stress including hypoxia and therapeutic hypothermia.1,2 Within a few weeks of birth, violaceous to erythematous indurated plaques develop on the back, buttocks, cheeks, or proximal extremities and generally self-resolve without scarring in weeks to months.3,4 Most cases can be diagnosed clinically; however, punch biopsy with sampling of subcutaneous fat is useful to confirm the diagnosis when needed. Histopathology demonstrates a lobular panniculitis with histiocytes, eosinophils, and multinucleated giant cells, and radial arrays of needle-like crystal cleft spaces are appreciated within adipocytes.3-6
Given the self-resolving nature of SCFN, in general, no active treatment is required.7-9 Supportive local wound care may be necessary if plaques ulcerate or if liquefactive bullae develop and drain.10 Analgesia should be provided for infants with painful skin lesions, escalating from acetaminophen7,11 to morphine.4,11,12
Importantly, SCFN is associated with the risk of potentially life-threatening hypercalcemia.1 Affected newborns should be monitored for hypercalcemia and caregivers should be educated about symptoms of hypercalcemia including irritability, vomiting, poor feeding, polyuria, hypotonia, hypertension, and seizures.1,4,13 Hypercalcemia in SCFN can result in nephrocalcinosis and renal failure.4,12,13
Calcium or vitamin D supplementation should be avoided for the first 3-6 months of life for all patients diagnosed with SCFN.7,8,14
Current recommendations suggest screening total serum calcium at the time of diagnosis of SCFN. As most cases of hypercalcemia in SCFN occur within the first 4 weeks of life,1 it is prudent to repeat total serum calcium levels at 2 weeks and 4 weeks after diagnosis of SCFN in an asymptomatic infant. Total calcium levels should be checked promptly if any infant with SCFN develops signs of hypercalcemia at any time. As delayed hypercalcemia can occur after SCFN lesions resolve, repeat total calcium screening is recommended for asymptomatic infants at 30, 45, and 60 days after skin resolution of skin lesions.1
If upon screening, asymptomatic infants with SCFN have hypercalcemia with total serum calcium level <12 mg/dL, parents should be educated on signs and symptoms of hypercalcemia and total serum calcium should be rechecked 1-2 times weekly until the calcium level is stable within normal range. After 2 consecutive weekly normal total serum calcium levels, it is reasonable to extend the interval of screening to every 2 weeks, then every 4-6 weeks until normalization of total calcium levels. Monitoring for possible delayed hypercalcemia after resolution of SCFN should be continued as above.
If total serum calcium is ≥12 mg/dL on screening or if symptoms of hypercalcemia are ...