A SURF1 gene mutation presenting as isolated leukodystrophy

Mitochondrial respiratory chain defects are increasingly recognized in pati ents with leukodystrophy. We report the first case of leukodystrophy with s ystemic cytochrome oxidase deficiency caused by a loss of function mutation in the SURF1 gene in a 2-year-old girl presenting with failure to thrive, global neurodevelopmental regression, and lactic acidosis. Although all pre viously reported mutations in the SURF1 gene have been found in patients wi th cytochrome oxidase (COX)-deficient Leigh syndrome, the phenotype associa ted with SURF1 protein deficiency should be extended to include leukodystro phy.