Hardened plaque on a neonate’s back


  • CA1011DermClin_Case2

A full-term, healthy female infant was born to a woman aged 24 years. It was the mother’s first pregnancy and was complicated by gestational diabetes and borderline hypertension. APGAR scores were 8 and 9, despite the presence of meconium staining at birth.

Two weeks after discharge, the infant was brought to the pediatrician because the mother was worried about a rash on the girl’s back. Examination revealed an irregular, lobulated, indurated 
7 x 9 cm plaque across the infant’s back; a smaller lesion was noted below the left axilla. The anterior trunk, extremities and face were spared.

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The answer is subcutaneous fat necrosis. A skin biopsy showed patchy fat necrosis surrounded by a granulomatous process consisting of histiocytes and multinucleated giant cells; needle-shaped clefts were present within the histiocytes and giant cells.1 These findings were consistent with...

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The answer is subcutaneous fat necrosis. A skin biopsy showed patchy fat necrosis surrounded by a granulomatous process consisting of histiocytes and multinucleated giant cells; needle-shaped clefts were present within the histiocytes and giant cells.1 These findings were consistent with the diagnosis of subcutaneous fat necrosis of the newborn (SFN). Laboratory studies were consequently ordered and serially followed.

Primarily seen in otherwise healthy full- or post-term infants, SFN is an uncommon, idiopathic, self-limited, inflammatory panniculitis. Although many infants with SFN are products of uncomplicated pregnancies via straightforward vaginal or cesarean deliveries, others have been subjected to stress or trauma related to labor and delivery.

Associated conditions include perinatal asphyxia, hypothermia, meconium aspiration syndrome, cord accidents, hypothermia, hypoglycemia, newborn failure to thrive, and such maternal complications as diabetes and pre-eclampsia.1-3

The onset of SFN is early, typically within the first few days to weeks of life, but it may be as late as two months.3 Commonly affected areas include the cheeks, buttocks, back, arms and thighs; there is a predilection to form over bony prominences. The anterior trunk is characteristically spared.2,3

Over time, affected areas progressively develop one or more localized, firm, smooth, and well-circumscribed areas of induration. Lesions may be small nodules or large plaques, and some are lobulated. The degree of overlying erythema is variable. Although typically painless, some lesions may cause the infant to cry when handled.

Lesions typically self-involute within several weeks to months without any sequelae. However, some become fluctuant as the fat necroses and liquefies, while other lesions calcify. Fluctuant lesions may be aspirated to decompress the area and promote resolution.1 Mild cutaneous atrophy may occur as a short-term consequence of SFN.

Although the pathogenesis of SFN is not well understood, it is hypothesized that an obstetric trauma or perinatal stress or hypothermia results in injury to the immature pannus, triggering fat necrosis. Some investigators have suggested that neonatal fat has a higher melting point than adult fat, affording it a greater propensity to solidify and crystallize under stress.2 The incidence of SFN is unknown. There is no apparent predilection for a specific ethnic or racial group, gender, or geographic region.1

Early histologic findings include perivascular inflammation and endothelial swelling. Later, fat necrosis with granulomatous changes consisting of histiocytes and multinucleated giant cells can be seen. The needle-shaped clefts and refractile crystals within the podocytes, histiocytes, and giant cells are thought to be attributable to triglycerides.1-3 Later in the disease, fibrosis develops as the lesions resolve; calcium deposition may be seen.

Although SFN is usually a banal, self-resolving process, rare complications — some of which are life-threatening — may occur and patients should be monitored. Hypercalcemia occurs during the resolution phase of this condition and is probably the most serious of the complications, which also include thrombocytopenia, hypoglycemia, hypertri­glyceridemia and infection.

Significant hypercalcemia may result in infant lethargy, irritability, hypotonia, polyuria, polydipsia, failure to thrive, seizures and cardiac arrest if not recognized and treated appropriately. Infants should be monitored with laboratory studies weekly or biweekly until the fat necrosis resolves. The time to resolution is typically one to six months.1-3

The pathogenesis of SFN-associated hypercalcemia is merely postulated. Staining of skin biopsy specimens has identified the presence of 25-hydroxyvitamin D3 1 alpha-hydroxylase within the granulomatous infiltrate. Investigators propose that the granulomatous process of SFN is responsible for excess production of 1,25-dihydroxycholecalciferol in a fashion analogous to such other granulomatous disease as sarcoidosis. Excessive vitamin D subsequently increases absorption of calcium, resulting in hypercalcemia.1-3

If hypercalcemia occurs, intervention is needed. Treatment includes hydration; judicial use of loop diuretics; and a low-calcium, low-vitamin-D diet. Corticosteroids, calcitonin, or bisphosponates may be of some benefit.

The differential diagnoses of SFN include sclerema neonatorum (SN), lipogranulomatosis, deep-tissue infection, and nodular panniculitis. The well-being of most infants with SNF — along with the histologic findings — readily distinguish it from these other conditions. SN is probably the most confusing early on, since it also occurs in the first few months of life. However, SN is more common in preterm infants than in term infants.4

Although both conditions affect the adipose tissue, skin findings are somewhat different. Unlike SFN, the skin lesions in SN are diffuse and consist of waxlike hardening of the subcutaneous tissue. The skin of infants with SN is bound to the underlying muscle and bone, whereas lesions of SFN are freely mobile.

Because of the self-limited, benign nature of SFN, most patients may be managed with supportive therapy and periodic monitoring. If lesions become fluctuant they may be aspirated to prevent rupture.

In this patient, initial monitoring demonstrated a slight thrombocytopenia that quickly resolved without sequelae. Calcium levels, monitored weekly, were always within the normal reference range.

The lesions on the infant’s back resolved, leaving a slight irregularity that could be found only on deep palpation. At her 12-month well-baby visit, only mild atrophic changes could be detected.

Maya Fetter, MD, is an intern in internal medicine at Carolinas Medical Center in Charlotte, N.C. Julia R. Nunley, MD, is professor of dermatology at Medical College of Virginia Hospitals, Virginia Commonwealth University, in Richmond. Neither author has any relationship to disclose relating to the content of this article.

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1. Burden AD, Krafchik BR. Subcutaneous fat necrosis of the newborn: a review of 11 cases. Pediatr Dermatol. 1999;16:384-387.

2. Tran JT, Sheth AP. Complications of subcutaneous fat necrosis of the newborn: a case report and review of the literature. Pediatr Dermatol. 2003;20:257-261.

3. UpToDate. Skin nodules in newborns and infants.

4. Aucharaz KS, Baker EL, Millman GC, Ball RJ. Neonatal subcutaneous fat necrosis with characteristic rash and hypercalcaemia. Arch Dis Child Fetal Neonatal Ed. 2007;92:F304. 

All electronic documents accessed October 11, 2011.

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