Following an uncomplicated pregnancy, labor, and delivery, a healthy 13-day-old girl presents for evaluation with a 2-day history of firm, violaceous nodules on her mid-upper back and right arm just above the axilla (Figure 1).
Subcutaneous fat necrosis of the newborn (SCFN) is an uncommon, benign disorder characterized by inflammation and necrosis of the subcutaneous fat tissue that typically presents in the first weeks of life in full-term and postterm infants.1 The etiology of SCFN is unknown but is thought to be linked to multiple neonatal and maternal risk factors including, but not limited to, perinatal hypoxia, meconium aspiration, therapeutic hypothermia, gestational diabetes, preeclampsia, maternal smoking, thrombosis, and dyslipidemia. Complications of SCFN include hypoglycemia, thrombocytopenia, hypertriglyceridemia, with the most critical being hypercalcemia.
Patients with hypercalcemia typically present with lethargy, hypotonia, irritability, vomiting, polyuria, polydipsia, constipation, and dehydration; however, some may be asymptomatic.1 There is debate about the underlying etiology of the development of hypercalcemia in neonates with SCFN. One proposed mechanism suggests increased activity of 1-alpha-hydroxylase on 25-hydroxyvitamin D by activated macrophages within the subcutaneous granulomas leads to excess intestinal calcium absorption.2,3 Another theory postulates that increased levels of inflammatory mediators, such as prostaglandin E, lead to activation of osteoclasts that release calcium from necrotic fat cells. At any rate, it is important to screen neonates with SCFN for hypercalcemia because, if severe and left untreated, it may lead to acute and chronic life-threatening effects on the cardiovascular and renal systems.2