Tender skin nodules in a newborn.

Subcutaneous fat necrosis of infancy is a rare disorder of subcutaneous adipose tissue that is sometimes complicated by hypercalcemia. Complete resolution is common. From the pediatrician's point of view, the disease is a rare but important cause of inconsolable cry in a newborn.

What was known?

Subcutaneous fat necrosis of newborn is a rare type of localized lobular panniculitis sometimes accompanied by hypercalcaemia and thrombocytopenia. The disease has a self-limiting course. The lesions stop appearing spontaneously and subsequently disappear over a period of months.

Introduction

Subcutaneous fat necrosis (SCFN) of newborn is a localized form of lobular panniculitis that is seen in a newborn in the first few weeks of life. The skin lesions may rarely be accompanied by hypercalcemia and thrombocytopenia. The disease usually has an excellent prognosis with complete resolution, except in a few cases with hypercalcemia. We report a newborn with SCFN with hypercalcemia who became asymptomatic after 3 weeks of birth.

Case Report

A 9-day-old male baby presented to us with an inconsolable cry. He was a full-term singleton delivered by cesarean section with a history of birth asphyxia. His mother had an uneventful antenatal period. Early postnatal events were otherwise normal, and the baby had been feeding well. The baby's crying aggravated on being handled or kept in the supine position. On examination, we found numerous tender purple-colored plaques and nodules over the back, buttocks, and upper thigh [Figure 1]. No other systemic abnormality that explained the crying was found on detailed examination. Routine blood, urine, and stool examinations were normal. Hypercalcemia was found, which persisted in spite of proper hydration and administration of frusemide in a dose of 1 mg/kg/body weight daily. A punch biopsy was done from a plaque over the back. Histology showed a normal epidermis. Lobular panniculitis was seen with a dense infiltrate of lymphocytes, histiocytes, and multinucleate giant cells [Figure 2].

Figure 1

Erythematous tender plaques and nodules on the back

Figure 2

Lobular panniculitis with lympho-histiocytic infiltrate with a few giant cells (H and E, ×40)

We started corticosteroid in the form of prednisolone (Dose-1 mg/kg/day in 2 divided doses orally). To relieve the pain, we prescribed acetaminophen (15 mg/kg/dose 4 times daily) and triclofos (50 mg/kg/dose). Breastfeeding was continued, and hydration was maintained. The baby gradually became symptom-free after 8 days of admission. Serum calcium level which was initially 12.4 mg/dl persisted for a week at that level before decreasing to 12 mg/dl at the end of 2 weeks and 11.4 mg/dl at the end of 4 weeks. The dose of prednisolone was gradually tapered over a period of 2 weeks, and the baby was discharged. Regular follow-up and routine check of serum calcium levels was done thereafter. The serum calcium levels decreased to 9.4 mg/dl at the end of 6 months and remained stable at that level thereafter. We followed him up for the next 18 months, and there was no recurrence till then.

Discussion

SCFN of infancy is a rare disorder of subcutaneous adipose tissue characterized by lobular panniculitis. The disease is transient in nature and often complicated by hypercalcemia.[1] Though the exact etiology is unknown, it has been postulated that SCFN of the newborn is caused by neonatal stress and hypothermia due to various causes. Due to hypothermia, neonatal subcutaneous fat may undergo crystallization, leading to adipocyte damage and a granulomatous reaction. Antecedent events, which are incriminated in the etiology of SCFN are forceps delivery, hypothermia, birth asphyxia, meconium aspiration syndrome, maternal pre-eclampsia, maternal diabetes, maternal high blood pressure, parathyroid hyperplasia, Rh factor incompatibility, protease inhibitor deficiency, cardiac surgery, deficiency of brown fat, defect in fat composition and metabolism, and exposure to active or passive smoking during pregnancy.[2]

Lesions of SCFN usually appear a few days or weeks after birth. Tender plaques and nodules which are small, indurated, and firm develop on the trunk, arms, thighs, buttocks, or cheeks. The lesions may be flesh-colored, or there may be an overlying erythema. If lesions are extensive, the skin may be fixed to the deeper structures and skin lesions may calcify and become rock hard on palpation. There may be pain of varying intensity in a quarter of the patients. The lesions may become fluctuant and ulcerate with spontaneous discharge of fat. They may evolve over a period of weeks with fresh crops appearing and persisting up to months. The disease has a self-limiting course, and the lesions ultimately stop appearing and disappear over a period of months.[3]

Though the exact pathogenesis is still unknown, various possible mechanisms have been postulated. According to one hypothesis, localized tissue hypoxia and mechanical pressure (augmented by thrombocytosis) and hypothermia result in necrosis and development of lesions. During birth, rough tissue handling by forceps or from obstetrician's hands etc., causes pressure on the bony pelvis, resulting in necrosis, which initiates the cascade.[4] Newborn fat has a higher percentage of the saturated palmitic and stearic acids in comparison to oleic acid. [5] Due to the higher melting point of these acids, the fat crystallizes early during a hypothermic episode. Thrombocytosis may also reduce blood circulation to an area, leading to local tissue hypoxia and hypothermia. [6] It has also been postulated that SCFN of newborn is a metabolic defect of neonatal fat or triglyceride, which is initiated by neonatal stress and is associated with elevated levels of prostaglandin E.[7]

The most common complication of SCFN is hypercalcemia, which may lead to death if uncontrolled.[8] There is preponderance of granulomatous macrophage around the skin lesion, and they may liberate 1, 25 dihydroxy cholecalciferol.[9] According to the another hypothesis, hypercalcemia is due to excessive bone resorption, which may occur due to elevated levels of prostaglandin E.[10]

Correlating the various observations, it may be postulated that hypothermia or hypoxia causes the subcutaneous fat of neonates to crystallize, leading to necrosis. There is an inflammatory infiltrate of cells including macrophages, which produces unregulated amounts of 1, 25 dihydroxy cholecalciferol, resulting in hypercalcemia.[11]

In cases, where a biopsy cannot be done, a fine needle aspiration may also show the typical cells. Polarized light microscopy shows the presence of doubly refractile crystals.[10]

SCFN of the newborn has to be differentiated from sclerema neonatorum, cold panniculitis, and calcinosis cutis due to causes other than SCFN. Sclerema neonatorum is a diffuse hardening of the skin in a sick premature newborn. Histologically, there is no necrosis of fat. Needle-shaped crystals may also be present in sclerema neonatorum, but the inflammatory infiltrate of lymphocytes, histiocytes, and multinucleated giant cells is absent. The prognosis is also poorer in sclerema neonatorum in contrast to SCFN. Cold panniculitis is limited to areas exposed to cold and was ruled out due to absence of history of exposure to cold. Considering the age of the patient and in the absence of any genodermatosis, systemic disorder or infection, other causes of calcinosis cutis were ruled out. In dystrophic calcification, the commonest type of calcinosis cutis, serum calcium is usually normal.[12]

SCFN of the newborn is a rare self-limiting disorder. Though it is a harmless condition, the associated hypercalcemia may cause significant morbidity and mortality. We used prednisolone orally for hypercalcemia because oral or intravenous steroids act by interfering with metabolism of vitamin D by converting it to the active form 1, 25 dihydroxyvitamin D and also inhibit the macrophage production of this metabolite.[10] Though subcutaneous calcitonin can also be used, it was not needed in this case because the hypercalcemia was controlled with steroids.[10] The rarity of case reports from India prompted us to report this case. Though our case had significant hypercalcemia, prompt and judicious treatment resulted in complete recovery within a period of 6 months.

What is new?

Though hypercalcaemia complicating a case of subcutaneous fat necrosis of newborn may cause significant morbidity and mortality, it was controlled in our case with prompt and judicious treatment with oral steroids and the patient recovered completely within 6 months.