Cytochrome c oxidase deficiency in three patients with Leigh's disease

Complementation analysis of systemic cytochrome oxidase deficiency presenting as Leigh syndrome

Systemic cytochrome oxidase deficiency presenting as Leigh syndrome is a well-defined biochemical entity. Although the enzyme defect is demonstrable in all tissues, clinical abnormalities are restricted to the central nervous system. Biochemical studies comparing rates of synthesis of cytochrome oxidase subunits with the steady-state levels of immunoreactive protein in the mitochondrial inner membrane suggest a defect in assembly or stability of the complex. Family studies suggest that the disease is inherited as an autosomal recessive and somatic cell genetic studies directly implicate nuclear genes. As there are likely to be a number of different nuclear genes involved in the synthesis, assembly and stability of the cytochrome oxidase complex, we have fused patient fibroblasts and analysed the heterokaryons for complementation of the enzyme defect in an attempt to define the extent of genetic heterogeneity in this condition. So far, three complementation groups have been defined, although the majority of patients fall into a single group.

Deficiency in complex IV (cytochrome c oxidase) of the respiratory chain, presenting as a leukodystrophy in two siblings with Leigh syndrome

Two siblings with Leigh syndrome presenting at the age of 6 months with clinical and radiological features suggestive of a leukodystrophy are reported. A deficiency in complex IV of the respiratory chain (cytochrome c oxidase) was demonstrated in muscle mitochondria of both patients. To our knowledge, this is the first familial case of Leigh syndrome due to cytochrome c oxidase deficiency, presenting clinically and radiologically with signs of a leukodystrophic process. We suggest that respiratory chain enzyme defects should be considered in the differential diagnosis of cases suggestive of a leukodystrophy.

Intracerebral distribution of mitochondrial abnormalities in 21 cases of infantile spongy dystrophy

Using a monoclonal antibody to an inner mitochondrial membrane antigen and light microscopic immunohistochemistry, we investigated the distribution of increased immunostaining (mitochondrial anomalies, MA) on paraffin sections from 21 brains with infantile spongy dystrophy (Leigh's disease, 8; Canavan's disease, 4; Alpers' syndrome, 2; mixed spongy dystrophy, 7). Compared with an age-matched control group, MA were present in all cases of Leigh's disease (leptomeningeal and intracerebral endothelial and vascular smooth muscle cells, choroid plexus epithelia, ependymal cells, astrocytes or some neurons), in 2 cases of Canavan's disease and the Alpers' syndrome cases (astrocytes and occasionally some neurons). The MA were restricted to spongy areas in Canavan's disease and Alpers' syndrome, whereas they were distributed throughout the brain in Leigh's disease. In mixed spongy dystrophies the Leigh histology was associated with MA, but not the Canavan histology. Brains with Wernicke's encephalopathy (3 cases), adult infarction (3), and multicystic encephalopathy (5) showed no MA, but one with methylmalonaciduria did. Our results substantiate the classification of Leigh's disease as primary mitochondrial encephalopathy.