Acylcarnitine profile mimicking multiple acyl-CoA dehydrogenase deficiency in a patient with mitochondrial myopathy and a mutation in MT-CO2

We present a 16-year-old girl with a life-long history of exercise intolerance. Laboratory investigations showed increased serum levels of acylcarnitines and increased urinary excretion of lactate and 2-hydroxyglutarate, consistent with multiple acyl-CoA dehydrogenase deficiency (MADD). Blood tests showed normal serum CK, increased liver transaminases and lactate, and mild anemia. Biochemical analyses of skeletal muscle mitochondria revealed an isolated and extremely low activity of cytochrome c oxidase (COX).