Mitochondrial encephalomyopathy: towards diagnosis. A case report.

Mitochondrial diseases may cause a wide range of central and peripheral nervous system disorders, as well as muscle disorders. The diagnostic workup routinely includes electrophysiological, morphological, neuroimaging and genetic studies. In some cases, the diagnosis may be ascertained only when mitochondrial DNA (mtDNA) examination in the muscle is performed. We report on a case of a 24-year-old woman, with a 7-year history of slowly progressive cerebellar syndrome and bilateral ptosis. Mitochondrial encephalomyopathy was suspected, based on the clinical picture and results of examinations, but the typical red ragged fibers were not found in the muscle biopsy. The results of molecular analysis of mtDNA showed a mtDNA deletion in the muscle and, on a level detectable only with polymerase chain reaction method, in blood leukocytes. This case emphasizes the important role of mtDNA studies in muscle in nonspecific multisystem mitochondrial disorders, even without clinical muscle involvement.