Spinal muscular atrophy-like picture, cardiomyopathy, and cytochrome c oxidase deficiency

The authors report a child with a spinal muscular atrophy (SMA)-like pictur e, cardiomyopathy, and cytochrome c oxidase (COX) deficiency. Electromyogra phy and muscle biopsy showed findings typical of SMA. However, COX staining of the muscle was negative. DNA analysis did not detect deletions in the s urvival motor neuron (SMN) gene. The lactate and lactate-to-pyruvate ratios were increased in blood and CSF. COX activity was decreased in muscle and fibroblasts. Western blot analysis showed reduced contents for all COX subu nits. Patients with clinical features resembling SMA but with an intact SMN gene should be screened for a mitochondrial disorder.