Diagnosis and treatment of mitochondrial myopathies

Abstract

Mitochondrial disorders are a heterogeneous group of disorders resulting from primary dysfunction of the respiratory chain. Muscle tissue is highly metabolically active, and therefore myopathy is a common element of the clinical presentation of these disorders, although this may be overshadowed by central neurological features. This review is aimed at a general medical and neurologist readership and provides a clinical approach to the recognition, investigation, and treatment of mitochondrial myopathies. Emphasis is placed on practical management considerations while including some recent updates in the field.

Figure 1.

Clinical features of mitochondrial myopathies, by organ system.

Figure 2.

Abnormalities on skeletal muscle biopsy in mitochondrial myopathy. Serial sections through vastus lateralis in a patient with mitochondrial myopathy showing: (A) haematoxylin and eosin, (B) cytochrome c oxidase histochemistry (COX) (note the COX deficient fibres), (C) succinate dehydrogenase histochemistry (SDH) (note the sub-sarcolemmal accumulation of mitochondria analogous to a ragged red fibre), and (D) sequential COX-SDH histochemistry showing a mosaic COX defect as seen in patients with mtDNA disorders.