Mitochondrial diseases are a very heterogeneous group of disorders affecting the nervous system, heart and skeletal muscle. The mutations are situated in nuclear DNA with Mendelian heredity and in mitochondrial DNA with maternal-type heredity.
We describe a natural clinical course, the results of biochemical and molecular genetic measurements from two siblings with mitochondrial disorders due to mutation 7512T>C in the gene for mitochondrial tRNA for serine. The mutation is associated with myoclonic epilepsy, deafness, ataxia, calcification in the basal ganglia and decreased cytochrome c oxidase activity.
The data should prove helpful in the exact diagnosis of patients with this phenotype.