Multiple symmetrical lipomatosis in mitochondrial disorders

Multiple symmetric lipomatosis (MSL) is characterized by enlarging, painless fat deposits in the neck and upper trunk. It is regarded as a benign proliferative disorder of adipose tissue. Recently a link with mitochondrial disorders has been suggested: 1. MSL occurs in patients with mitochondrial DNA (mtDNA) mutations 2. Mitochondrial abnormalities have been shown in some MSL patients. It has been suggested that MSL is a speciphic disorder of brown adipose tissue (BAT) based on the typical distribution and morphological and biochemical findings on cultured adipocytes obtained from lipectomy. BAT is peculiarly enriched in mitochondria and shows a highly active oxidative metabolism. We present two families with mitochondrial encephalomyopathy in which MSL is associated with two different mtDNA point mutations in the same gene: In family 1, several members harboring the A8344G in tRNA gene mutation presented unilateral or bilateral lipomas. The abundance of the mutation could be correlated to the clinical presentation of the lipomas. In Family 2 MSL was associated to multisystem involvement and a G8363A mutation in the same gene. We propose that due to mitochondrial dysfunction, BAT adipocytes could undergo to progressive lipid accumulation proliferation eventually leading to MSL.