Subcutaneous fat necrosis of the newborn

Published on 18/03/2015 by admin

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Last modified 18/03/2015

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Subcutaneous fat necrosis of the newborn

Bernice R. Krafchik

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

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Subcutaneous fat necrosis (SFN) of the newborn is a rare, self-limited skin disease that occurs in the first few weeks of life. It affects areas where fat tissue is found and presents with a typical clinical picture of erythema and induration, commonly over the extremities, back, buttocks, and thighs. Individual lesions vary from a few millimeters to several centimeters and may coalesce. The exact etiopathogenesis is unclear but most infants suffer from some form of perinatal difficulty that includes asphyxia, peripheral hypoxemia, meconium aspiration or trauma; it is also seen in association with maternal diabetes. There have been a number of recent articles describing SFN in infants who have been treated with total body cooling for hypoxic ischemic encephalopathy (HIE). It is unlikely that the HIE is the cause of the SFN as it has also has been described in patients receiving hypothermia for cardiac surgery. Most infants with SFN have been delivered by cesarean section which makes birth trauma an unlikely cause.

The main and important complication seen with SFN is hypercalcemia, which occurred in one-third of patients who were admitted to hospital for SFN. The cause of the hypercalcemia is unknown; one theory postulates that increased calcium absorption occurs as a result of unregulated extrarenal production of 1,25-dihydroxyvitamin D. In cases of severe hypercalcemia seizures and death may ensue, in addition to nephrocalcinosis and hypercalciuria. Other symptoms of hypercalcemia are usually non-specific and consist of fever, vomiting, lethargy, constipation, feeding difficulties, and failure to thrive. Rarely, thrombocytopenia, hypoglycemia, anemia, hypervitaminosis D, and hypertriglyeridemia may also be seen.

SFN resolves spontaneously within 3 to 6 months, leaving normal skin or small pitted scars, and occasionally an absence of fat tissue in the affected areas. Treatment is seldom necessary, except in the rare instances when liquefaction of the fat tissue occurs, or when hypercalcemia or other blood chemistry abnormalities develops.

Management strategy

Biopsy, with its characteristic pathology, is usually not warranted as the clinical picture is typical. Aspiration cytology can be helpful in establishing the diagnosis. It is a simple alternative to a biopsy with lesions that are not clinically diagnostic. MRI scans and ultrasound demonstrate characteristic features and highlight nephrocalcinosis and other areas of calcification if present. In patients with SFN it is important to perform blood sampling looking for abnormal calcium values. Serum calcium levels may be low in normal infants and in patients with SFN during the first 2 weeks of life. Infants with SFN should have calcium values checked weekly, or, if there is any increase in serum calcium, bi-weekly for up to 6 months. If the infant is sick, tests for other abnormal blood indices should be performed.

Treatment regimens are determined by the levels of hypercalcemia, and hypercalciuria. If serum levels are marginally raised, monitoring the serum and urine calcium may be all that is necessary and a spontaneous return to normal levels often occurs. If the increased levels persist or rise further, treatment should be instigated. Mild hypercalcemia is treated by the withdrawal of vitamin D and by using a low-calcium diet. This is best accomplished by breastfeeding, as breast milk is low in both vitamin D and calcium. If this is not possible or helpful, a formula low in calcium with no vitamin D should be considered, and if a reduction in calcium does not occur or the levels continue to rise intravenous saline at 1.5 times the maintenance requirement is given, to promote the renal excretion of calcium. This is augmented with furosemide (a diuretic drug), which further promotes excretion. Other options for non-responders include calcitonin (4–8 IU/kg every 6 to 12 hours), bisphosphonates (pamidronate and others), and oral corticosteroids (hydrocortisone or prednisone). The latter treatments should be instituted with the help of a pediatric endocrinologist. The rare occurrence of liquefaction in the lesions is treated by removal of the liquid with a large-bore needle.