Children frequently undergo muscle biopsy for the workup of hypotonia
under general anaesthesia which poses unique risks in patients with un
diagnosed muscle disease. Mitochondrial myopathies are a relatively ne
wly recognized cause of myopathy and multisystem disease in both adult
s and children. The diagnosis is complex. In addition to causing myopa
thy, there are metabolic derangements present in some cases that may b
e life-threatening We present three cases of children with hypotonia w
here 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 discus
sed.