[Mitochondrial myopathies]

The organ most frequently affected in mitochondrial disorders is the skeletal muscle (mitochondrial myopathy). Mitochondrial myopathies may be part of syndromic as well as non-syndromic mitochondrial disorders. Involvement of the skeletal muscle may remain subclinical, may manifest as isolated elevation of the creatine-kinase, or as weakness and wasting of one or several muscle groups. The course of mitochondrial myopathies is usually slowly progressive and only rarely rapidly progressive leading to restriction of mobility and requirement of a wheel chair or even muscular respiratory insufficiency. Frequently reported symptoms of mitochondrial myopathies are permanent tiredness, easy fatigability, muscle aching at rest or already after moderate exercise, muscle cramps, muscle stiffness, fasciculations and muscle weakness. The diagnosis is based on the history, clinical neurologic examination, blood chemical investigations, lactate stress test, electromyography, magnetic resonance imaging, magnetic resonance spectroscopy, muscle biopsy, biochemical investigations of the skeletal muscles, and genetic investigations. Only symptomatic therapy is available and includes physiotherapy and orthopedic supportive devices, diet, symptomatic drug therapy (analgetics, cramp-releasing drugs, antioxidants, lactate-lowering drugs, alternative energy sources, co-factors), avoidance of mitochondrion-toxic drugs, surgery (correction of ptosis or orthopedic problems), and invasive or non-invasive mechanical ventilation. General anesthesia needs to be performed in the same way as in patients with susceptibility for malignant hyperthermia.