Subcutaneous Fat Necrosis of the Newborn

Updated: Apr 04, 2016
  • Author: Sungat K Grewal; Chief Editor: William D James, MD  more...
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Overview

Background

Subcutaneous fat necrosis of the newborn (SFNN) is an uncommon disorder characterized by firm, mobile, erythematous nodules and plaques over the trunk, arms, buttocks, thighs, and cheeks of full-term newborns. [1, 2] The nodules and plaques appear in the first several weeks of life. Subcutaneous fat necrosis of the newborn usually runs a self-limited course, but it may be complicated by hypercalcemia and other metabolic abnormalities. [1, 2]

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Pathophysiology

The exact pathogenesis of subcutaneous fat necrosis of the newborn (SFNN) is not known. It is postulated that cold or stress-induced injury to immature fat cells results in the development of solidification and necrosis. A granulomatous infiltrate forms, which, through various pathways, may lead to life-threatening hypercalcemia. Staining of biopsy specimens demonstrates increased levels of 1alpha-hydroxylase within the granulomatous infiltrate, as is seen in other granulomatous conditions such as sarcoidosis. [3] Alpha-hydroxylase promotes the conversion of 25 OH D3 to its active form 1,25 OH 2D3; the latter increases intestinal absorption of calcium and calcium mobilization from bones, potentially leading to hypercalcemia. [1, 4, 5] Elevated levels of prostaglandin (PG) E2 have been reported in subcutaneous fat necrosis of the newborn. [6] and may contribute to hypercalcemia through a different pathway.

Alternative explanations for hypercalcemia include the release of calcium from necrotic fat cells or elevated parathyroid hormone (PTH) levels that indirectly increase serum calcium by promoting osteoclast activity. [7] A child with cyanotic heart disease treated with prostaglandins (intravenous PGE1) to maintain patent ductus arteriosus developed subcutaneous fat necrosis of the newborn; when the PGE1 was discontinued, the subcutaneous fat necrosis of the newborn resolved. [6] Elevated prostaglandins contribute to the inflammatory cascade that follows, marked by thrombocytopenia, high acute-phase reactants such as C-reactive protein, and fever. [8, 9] The latter has been attributed to increased levels of PGE2 and granuloma production of interleukin 1.

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Epidemiology

Frequency

Frequency is unknown; subcutaneous fat necrosis of the newborn (SFNN) is rare.

Race

Race does not play a role.

Sex

Sex does not play a role.

Age

Subcutaneous fat necrosis of the newborn (SFNN) occurs in the first several weeks of life. [1, 2, 4] Hypercalcemia, if it occurs, begins in children aged 1-2 months.

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