Mitochondrial functions in chronic spinal muscular atrophy.

We determined the respiration rate, respiratory control and ADP/O ratios, with different substrates in mitochondria isolated from seven patients with chronic spinal muscular atrophy and compared them with normal human muscle. In all cases studied, a severe alteration of the respiratory control with variable derangement of oxidative phosphorylation was found. Similar findings have been described in other neuromuscular disorders including the so-called "mitochondrial myopathy". We believe that this disturbance of mitochondrial function is non specific and only the hypermetabolic syndrome of Luft could be considered biochemically as a "mitochondrial myopathy", a disorder selectively involving mitochondria of skeletal muscle.