Mitochondrial myopathies: an unusual cause of hypotonia in infants and children.

Children frequently undergo muscle biopsy for the workup of hypotonia under general anaesthesia which poses unique risks in patients with undiagnosed muscle disease. Mitochondrial myopathies are a relatively newly recognized cause of myopathy and multisystem disease in both adults and children. The diagnosis is complex. In addition to causing myopathy, there are metabolic derangements present in some cases that may be life-threatening. We present three cases of children with hypotonia where the diagnosis was suspected in two patients, and confirmed in the third. The question of whether patients with mitochondrial myopathies are at increased risk for developing malignant hyperthermia is discussed.