A large-scale deletion of mitochondrial DNA in a case with pure mitochondrial myopathy and neuropathy.

Here we report the findings from a male patient with myopathy and neuropathy, who has a large-scale deletion of the mitochondrial genome at nucleotides 6570-14150. In the patient's history, muscle cramps with intermittent weakness and polyneuropathy with disturbed micturition were the predominant symptoms. Morphological examination of a muscle biopsy sample revealed numerous ragged red fibers and prominent paracrystalline intramitochondrial inclusions. The sural nerve biopsy sample disclosed a chronically progressive neuropathy, predominantly axonal in type with a minor demyelinating component. In previous studies the clinical symptoms mentioned above have been related to point mutations at various positions in the mitochondrial DNA (mtDNA). The present study is the first to describe a large (8 kb) deletion of the mtDNA which had apparently caused myopathy and polyneuropathy without encephalopathy.