A boy with muscle weakness, hypercarbia, and the mitochondrial DNA A3243G mutation.

The point mutation in the mitochondrial genome tRNA(Leu_ (A3243G) is associated with the syndrome of mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS). We report a boy presenting with respiratory compromise and hypercarbia owing to severe muscle weakness. Historically, he demonstrated idiopathic growth hormone deficiency, retarded bone age, and exercise avoidance. Owing to severe respiratory compromise out of proportion to expected recovery, a metabolic work-up was performed. Muscle biopsy demonstrated abnormal mitochondria structure and heteroplasmic A3243G mutation. Idiopathic growth hormone deficiency and retarded bone age have not been previously reported in MELAS, and these findings delayed testing for mitochondrial disease. This case demonstrates that isolated muscle weakness in the context of other organ system abnormalities should make the investigator consider MELAS. (J Child Neurol 2006;21:77-79).