FDG uptake in lipomatous hypertrophy of the interatrial septum is not likely related to brown adipose tissue.

Lipomatous hypertrophy of the interatrial septum (LHIS) may be associated with arrhythmias or sudden death. Increased fluorine-18 fluorodeoxyglucose (FDG) uptake in LHIS is occasionally found on positron emission tomography, and has been attributed to metabolically active brown adipose tissue (BAT) contained within LHIS. We report a case of a patient suggesting that neither of the 2 currently known mechanisms of glucose uptake by BAT is responsible for FDG uptake in LHIS, unless a mechanism of BAT activation exists that has not been previously described. This study also suggests that FDG uptake is unlikely to be due to cardiomyocytes contained within LHIS. Inflammation is a potential mechanism, although further investigation is needed.