GENETIC-COUNSELING AND PRENATAL-DIAGNOSIS IN DISORDERS OF THE MITOCHONDRIAL ENERGY-METABOLISM

Point mutations in mitochondrial DNA, as found in MELAS, MERRF, NARP a nd other syndromes, are inherited via the maternal lineage. Genetic co unselling can be beneficial, but prenatal diagnosis is not advantageou s in these syndromes. Empirical data about the recurrence risk can be applied in Leber disease (LHON). Mitochondrial disorders not associate d with a point mutation have a sporadic nature (large deletions/duplic ations in mitochondrial DNA) or are transmitted according to Mendelian laws. Autosomal dominant inheritance is likely to be found in disorde rs with depletion of mitochondrial DNA. X-linked mode of inheritance i s seen in Menkes disease, Earth syndrome, and in deficiencies of the E (1) alpha subunit of the pyruvate dehydrogenase complex. Mutation anal ysis or linkage studies can be applied for carrier detection and prena tal diagnosis in these three types of mitochondriopathies. The majorit y of the disorders with a disturbed mitochondrial energy metabolism ar e likely inherited in an autosomal recessive mode. Prenatal diagnosis can be performed in the cases of cytochrome c oxidase and NADH dehydro genase deficiencies in chorionic villi in selected families.