Subcutaneous fat necrosis of the newborn (SFNN) is a rare, benign skin condition that affects newborns, typically those born at term or post-term. It involves the hardening of fatty tissue located just beneath the skin. Though concerning in appearance, SFNN is generally self-resolving and often disappears on its own over time.
Recognizing Subcutaneous Fat Necrosis
SFNN typically presents as firm, well-demarcated nodules or plaques on the skin. These lesions can range in color from reddish to purplish or may appear skin-colored. Upon touch, they feel indurated and rubbery, sometimes described as woody hard. The size of these nodules can vary, from a single small lesion of 1 cm to multiple larger areas exceeding 8 cm in diameter.
Common locations for SFNN lesions include the back, shoulders, buttocks, thighs, arms, and cheeks. The abdomen and chest are not typically affected. The condition usually becomes noticeable within the first few weeks of life, within the first four weeks. While the lesions are often asymptomatic, they can occasionally be tender during the acute phase.
Understanding the Causes
The underlying mechanism of subcutaneous fat necrosis involves injury or stress to the fat cells. This often stems from factors related to cold exposure, tissue hypoxia (lack of oxygen), or trauma experienced during or shortly after birth. SFNN is linked to various perinatal stressors, not parental neglect or fault.
Several associated risk factors contribute to the development of SFNN. These include perinatal asphyxia (lack of oxygen at birth), hypothermia (low body temperature), difficult or traumatic deliveries, and meconium aspiration syndrome. Maternal conditions such as preeclampsia or diabetes, certain medications given to the mother or infant can also play a role. Therapeutic hypothermia, used for neuroprotection, has also been identified as a risk factor.
Medical Care and Outlook
Diagnosis of SFNN is primarily clinical, relying on visual examination and palpation of the characteristic skin lesions. While a skin biopsy can confirm the diagnosis by revealing specific changes in fat cells, it is rarely needed. Imaging techniques, such as ultrasound, can also be useful in identifying the subcutaneous changes.
The management approach for SFNN is largely conservative and supportive, as lesions typically resolve on their own. Gentle skin care is recommended. The nodules often disappear spontaneously over several weeks to months, usually without scarring or atrophy. In cases where large nodules become fluid-filled, needle aspiration may be considered to prevent rupture and potential scarring, though this is seldom necessary.
The prognosis for infants with SFNN is generally favorable, with most cases resolving completely without specific treatment. Regular monitoring of the infant’s overall health and the appearance of the lesions is usually the main course of action.
Addressing Potential Complications
While subcutaneous fat necrosis of the newborn is largely benign, a rare potential complication is hypercalcemia, an elevated level of calcium in the blood. This can occur as fat cells break down, releasing calcium into the bloodstream. Increased prostaglandin activity and macrophage secretion from the lesions also contribute to higher calcium levels.
Symptoms of hypercalcemia include poor feeding, vomiting, lethargy, irritability, and muscle weakness. Other signs include frequent urination, increased thirst, and poor weight gain. It is important to monitor calcium levels regularly, especially for infants with extensive lesions, as hypercalcemia can lead to serious issues such as kidney injury. While extremely rare associations like hypoglycemia or thrombocytopenia have been noted, hypercalcemia remains the primary concern requiring close medical attention.