Lipomatosis, proximal myopathy, and the mitochondrial 8344 mutation. A lipid storage myopathy?

Multiple symmetric lipomatosis (MSL) has been related in some cases to the 8344 point mutation of the tRNA-lysine gene of the mitochondrial DNA, mainl y in the context of families with classic myoclonic epilepsy with ragged-re d fibers (MERRF) and exceptionally in patients with proximal myopathy as th e only manifestation of mitochondrial disease. We report on two families ha rboring the 8344 mutation. The patients presented with MSL and myopathy, ex pressed as limb girdle weakness in index cases and as exercise intolerance in the others. All muscle biopsies performed showed lipid storage apart fro m RRF and respiratory chain complexes deficiency. A possible explanation fo r both adipose proliferation and lipid storage myopathy in these cases is a disturbance in intermediary lipid metabolism secondary to mitochondrial re spiratory chain deficiency that could be related via carnitine deficiency. (C) 2000 John Wiley & Sons, Inc.