Subcutaneous fat necrosis: Report of two cases
Dermatology Department, Habib Thameur Hospital, Tunis, Tunisia. email@example.com
Subcutaneous fat necrosis of the newborn is an uncommon, benign process in full-term infants or postmature neonates who experienced a perinatal distress. It is a transient condition of unknown origin; however, hypercalcemia may be a potentially life-threatening complication of this otherwise self-healing process. We report two cases of subcutaneous fat necrosis and discuss the clinical features, etiology, and complications of the disease.
Subcutaneous fat necrosis (SFN) is a rare, temporary, self-limited pathology affecting adipose tissue of full-term or postmature neonates [1, 2]. This entity usually occurs in the first weeks following a complicated delivery. Even though spontaneous resolution without sequelae is the norm, patients should be followed for development of late complications of SFN, especially hypercalcemia . We report two cases of SFN of the newborn observed over a 13-year period in our dermatology department.
The first patient was a 3-kg, full-term infant girl, born after 1 hour of labor by a spontaneous normal delivery. On the second day the baby developed firm, violaceous plaques of the back, shoulders, buttocks, arms, and legs (Fig. 1). On day 3 the lesions of the back became fluctuant with a spontaneous drainage revealing a chalky nonpurulent substance (Fig. 2). A skin biopsy revealed normal epidermis with an inflammatory granuloma of the hypodermis; there were giant cells and lipophages with needlelike crystals within adipocytes (Fig. 3). Normal laboratory findings excluded hypercalcemia. After 20 days the newborn was a well-appearing infant with a spontaneous regression of the lesions. At age 3 months, the patient showed only mild scarring at the site of the drainage.
The patient is a 3-kg male infant born at 40 weeks of gestation. The baby was born by a normal delivery, but he developed respiratory distress requiring 1 day of ventilatory support. The clinical examination at day 13 showed nontender, firm, violaceous subcutaneous nodules localized to the arms, forearms, thighs, legs, palms, and soles (Fig. 4). In several areas the nodules coalesced into extensive plaques. The histological examination showed the same characteristic findings as in the first case. The lesions resolved in 3 months without scarring.
SFN is an acute hypodermatitis that occurs soon after birth, usually within the first 4 weeks of life. About 200 cases have been reported , with only three previous Tunisian observations . This rare panniculitis is commonly found in full-term or postmature infants after a difficult delivery, as with our second patient. Usually, the clinical diagnosis is evident without need for histologic confirmation. Characteristic lesions comprise painless, subcutaneous, indurated, mobile nodules or well-defined inflammatory plaques. The overlying skin may be violaceous, erythematous, or normal in color. The back, the buttocks, the thighs, the arms, and cheeks are typical sites of involvement. As observed in our first patient, the lesions are sometimes fluctuant with liquefied fat and mild atrophy of the skin. When the clinical diagnosis is not typical, the histopathological features are helpful .
Biopsy specimen of SFN demonstrates necrosis of the fat, abundant histiocytes, multinucleated giant cells with granuloma formation, and lipocytes with radially arranged needle-shaped clefts. Fine-needle aspiration of the subcutaneous lesions has been reported as an alternative to skin biopsy to establish the diagnosis . SFN most often undergoes spontaneous resolution within several weeks but may last as long as 6 months. However, extracutaneous manifestations sometimes occur, and the patient should be evaluated and monitored for hypoglycemia, hypertriglyceridemia, anemia, thrombocytopenia, and (most importantly) hypercalcemia [3, 5]. Hypercalcemia is considered to be an uncommon complication, but to date it is the one most frequently reported. Hypercalcemia appears within 1-6 months after the onset of skin lesions. Hypercalcemic infants may manifest lethargy, irritability, hypotonia, vomiting, polyuria, polydipsia, dehydration, constipation, and failure to thrive. Some authors suggest a correlation between hypercalcemia and other parameters such as short duration of pregnancy, low birth weight, and hypocalcemia in the first days of life [3, 6].
The main clinical differential diagnosis is sclerema neonatorum (SN). Although the association of SN and SFN has been reported in a neonate, several features distinguish between SFN and SN, such as the age of onset, the distribution and extent of lesions, and a poor general status of the baby . Other diagnoses that should also be considered in a neonate with abnormalities of the subcutis include cytomegalovirus infection, congenital lymphedema, SN-like changes, fibromatosis, and hemangioma .
The cause of this disease remains unknown, but several hypothesis have been presented. Suggested etiologies include fetal factors such as a primary defect in subcutaneous fat, perinatal complications (especially ischemic injury), local trauma, hypothermia or birth hypoxia (as with our second patient), and maternal disorders such as gestational diabetes, preeclampsia, or maternal exposure to cocaine or calcium antagonists . Prostaglandin E has also been implicated in the pathophysiology of SFN in the setting of hypoxia and hypoperfusion, but it is likely that both lipids and prostaglandin E act as mediators in SFN rather than serving as etiologic factors . A recent series reporting ten children born by Caesarian section, who presented with SFN, cast some doubt on the suggested role of trauma in initiating SFN; delivery by Caesarian section is often less traumatic than vaginal delivery. For our first patient the triggering factor could have been trauma during labor. For the second patient, SFN is probably the result of decreased tissue perfusion from a day of hypoxia.
SFN is a benign condition that does not require treatment. Patients should be followed for up to 6 months after the appearance of the skin lesions to detect manifestations of hypercalcemia.
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