Laura C Cleary, MD

	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.

 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.

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	Patients with hypercalcemia typically present with lethargy, hypotonia, irritability, vomiting, polyuria, polydipsia, constipation, and dehydration; however, some may be asymptomatic.

 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.

 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.

	With SCFN, painful, indurated, erythematous-violaceous nodules or plaques present on the arms, shoulders, back, and less commonly on the face, legs, and buttocks, in the first weeks of life.

 It is categorized as a localized form of lobular panniculitis.

 The differential diagnosis of lobular panniculitides is narrow in this age group, including sclerema neonatorum, traumatic panniculitis (eg, forceps delivery), and poststeroid panniculitis in addition to SCFN. Distinguishing SCFN and sclerema neonatorum is based on histopathologic review and clinical history. Needle-shaped crystals in a radial arrangement are a characteristic histologic feature present in both conditions (Figure 3).

	The 2 conditions are distinguished by an absence of an inflammatory infiltrate in sclerema neonatorum that is normally present in SCFN.

 Sclerema neonatorum usually presents as diffuse hardening of the skin in severely ill, hypoxic, septic, and premature infants. Poststeroid panniculitis occurs typically in children on high-dose systemic steroids whose doses were rapidly decreased or steroid therapy abruptly stopped. The cutaneous findings appear roughly 1 to 10 days after cessation of the high-dose systemic steroids and typically manifest on the cheeks because this area is where the most accumulation of fat is induced by steroids. Additionally, SCFN can be distinguished from poststeroid panniculitis based on the clinical history; however, a biopsy may still be used to differentiate the 2 diagnoses if necessary.

	Subcutaneous fat necrosis of the newborn is generally a benign, self-limiting disorder that resolves in a period of weeks to months. The management strategy includes monitoring metabolic derangements, specifically, frequent monitoring of calcium levels.

 Subtle chronic hyperglycemia may persist for 4 to 6 months. Treatment of severe hypercalcemia generally includes intravenous isotonic fluids, loop diuretics, and corticosteroids. Di Bari and colleagues implemented zoledronic acid, a bisphosphonate, in a patient who was refractory to standard treatments.

 However, most patients without severe hypercalcemia improve without treatment.

	The patient’s initial chemistry profile demonstrated a mildly elevated calcium of 10.9 mg/dL (normal range, 8.7-10.4 mg/dL). Dermatology was consulted. A punch biopsy showed necrotic adipocytes containing needle-shaped crystals in a radial arrangement typical of subcutaneous fat necrosis (Figure 2).

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	The patient’s mother and grandmother were educated regarding her condition and reassured that her lesions would improve over weeks to months. At her 2-week follow-up, her calcium level was stable at 10.8 mg/dL and her lesions were noted to be smaller. At the 4-month follow-up, the patient’s lesions were barely palpable.

	1. Rubin G, Spagnut G, Morandi F, Valerio E, Cutrone M. Subcutaneous fat necrosis of the newborn. 

	2. Canpolat N, Özdil M, KuruÄoÄlu S, ÇalÄ±Åkan S, Sever L. Nephrocalcinosis as a complication of subcutaneous fat necrosis of the newborn. 

	3. Shumer DE, Thaker V, Taylor GA, Wassner AJ. Severe hypercalcaemia due to subcutaneous fat necrosis: presentation, management and complications. 

	4. Del Pozzo-Magaña BR, Ho N. Subcutaneous fat necrosis of the newborn: a 20-year retrospective study. 

	5. Coondoo A, Lahiry R, Choudhury A, Sengupta S. Tender skin nodules in a newborn. 

	6. Requena L, Sánchez Yus E. Panniculitis. Part II. Mostly lobular panniculitis. 

	7. Di Bari JA, Nead JA, Schurman SJ. Zoledronic acid for neonatal subcutaneous fat necrosis. 

	Mrs. Ward is a fourth-year medical student at the Medical College of Georgia, Augusta University, Augusta, Georgia. Dr Cleary is a third-year Dermatology resident, Division of Dermatology, Medical College of Georgia, Augusta University, Augusta. Dr Davis is professor and chief of Dermatology and Residency Program director for the Division of Dermatology, Medical College of Georgia, August University, Augusta. Dr. Cohen, section editor for Dermcase, is professor of Pediatrics and Dermatology at Johns Hopkins University School of Medicine, Baltimore, Maryland. The authors and section editor have nothing to disclose in regard to affiliations with or financial interests in any organizations that may have interest in any part of this article. Vignettes are based on real cases that have been modified to allow the authors and editor to focus on key teaching points. Images also may be edited or substituted for teaching purposes.

Articles

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.

Author | Laura C Cleary, MD

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