P2A288: Atypical Subcutaneous Fat Necrosis Occurring After Therapeutic Hypothermia and Extracorporeal Membrane Oxygenation

Introduction: Subcutaneous fat necrosis of the newborn (SCFN) is a rare panniculitis typically affecting term and post-term neonates, theorized to be secondary to decreased skin perfusion, and known to be associated with vasoconstrictive processes such as ischemic injury and therapeutic hypothermia (TH). Though usually self-limited, it can cause life-threatening hypercalcemia. To our knowledge, only one other case of SCFN occurring after TH and extracorporeal membrane oxygenation (ECMO) has been reported in the literature. We present the second case.

Case Description: A 37-week male infant was admitted to the NICU for respiratory failure. He was born to a Gravida 4 Para 1, serology negative mother with a history of fetal demise. Decreased fetal heart tones resulted in a failed vacuum extraction and subsequent stat cesarean section. APGARs were one, two, and four at one, five, and ten minutes, respectively. The infant required positive pressure ventilation and intubation in the delivery room. In the NICU, he was placed on conventional mechanical ventilation and TH was initiated for severe hypoxic ischemic encephalopathy. He also received volume and vasopressors for hypotension and antibiotics for presumed sepsis. Shortly after admission, he experienced cardiopulmonary arrest requiring chest compressions, epinephrine, calcium, and bicarbonate. An echocardiogram showed severe biventricular dysfunction, necessitating placement on veno-arterial (VA) ECMO. TH was continued for a total of 72 hours through the ECMO circuit. On day of life 15, multiple erythematous and indurated skin lesions appeared on the left heel, concerning for SCFN versus an infectious etiology. In following days, similar lesions also appeared on the back, occiput, chest, abdomen, face, and extremities (Figures 1 and 2). A skin biopsy was performed and revealed scanty subcutaneous adipose tissue with adipocytes demonstrating needle-like crystals, fibrotic dermis with a histiocytic and patchy neutrophilic infiltrate, scattered ectatic vessels, and negative infectious stains; consistent with SCFN. At 3.5 months, he was discharged on room air with a gastrostomy tube. He never had hypercalcemia or other sequelae of SCFN. At his 5-month follow-up visit, all skin lesions were resolving.

Discussion: This is the second reported case of SCFN occurring after TH and ECMO and the first with an atypical lesion location. ECMO is a form of cardiopulmonary support that aids perfusion to tissues, including the skin. This, in theory, should mitigate the risk of developing SCFN. SCFN typically occurs over bony prominences of the buttocks and back with sparing of the chest and abdomen. However, our patient had uniquely located lesions on his chest and abdomen.

Conclusion: SCFN should remain in the differential diagnosis for erythematous and indurated skin nodules and plaques occurring after TH and ECMO, even if they occur in atypical locations.