BENIGN MITOCHONDRIAL MYOPATHY WITH DECREASED SUCCINATE CYTOCHROME-C REDUCTASE-ACTIVITY

In most of the cases previously described, the defect on complex II wa s suggested by low activity of succinate cytochrome C reductase (SCCR) . The clinical pattern of the previous 10 cases is heterogeneous and m ay be limited to one particular tissue or be of a more general nature. We report a 22-year-old-woman, daughter of consanguineous parents, wi th generalized muscle weakness, easy fatigability and benign course, w ho showed a decrease of SCCR activity in mitochondria of muscle fibers . Free carnitine (FC) concentration was decreased in muscle as well. T he muscle biopsy showed a mild variation in fiber size, with fiber typ e I predominance, subsarcolemmal oxidative DPNH accumulations, excess of neutral lipids and abnormally large mitochondria with paracrystalli ne inclusions. A possible inheritance pattern is discussed. Coenzyme Q 10 therapy in this patient induced a significant increase of global MR C index score and a decrease of the turns-mean amplitude ratio in the automatic analysis of the EMG.