Involvement of Brown Adipose Tissue in Subcutaneous Fat Necrosis of the Newborn

Background: Subcutaneous fat necrosis (SCFN) of the newborn is a rare condition that manifests within days after birth. The interscapular region, axillae and shoulders are the most commonly affected sites, corresponding to anatomic sites of brown adipose tissue (BAT) in newborns. Objective: We postulated a specific involvement of BAT in SCFN and searched for brown adipocytes at affected sites. Methods: Biopsy specimens were immunostained with antibodies against uncoupling protein 1 (UCP-1) and examined by electron microscopy. We also examined BAT by 18 F-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography and computed tomography (PET-CT) scanning. Results: A few cells in biopsy specimens from two patients bound antibodies against UCP-1, and brown adipocytes were detected at several stages of degeneration. PET-CT scans revealed lower uptake of 18 F-FDG at major sites of SCFN. Conclusion: SCFN and BAT can be found at the same sites, suggesting a pathophysiological connection.