[Diagnosis and therapy of mitochondriopathies]

Defects of the mitochondrial energy production cab be expressed in many tissues and may lead to various types of diseases. Since defects can occur on many sites of the oxidative phosphorylation system, molecular diagnosis can be difficult. In typical mitochondrial syndromes, like MELAS- or MERRF-syndrome, diagnosis can be suspected already on clinical grounds. Lactate measured in various body fluids is still the best selective screening parameter. Loading tests, respectively ergometry is only necessary in the milder clinical forms of diseases or possibly in older children. The in vivo lactate determination e.g. In the CNS by 1H NMR spectroscopy can be helpful in evaluating prognosis. The diagnosis of a mitochondriopathy is usually confirmed enzymatically by tissue biopsies; skeletal muscle is still the tissue of the first choice because some enzyme deficiencies are not sufficiently expressed in cultured fibroblasts. If possible, intact mitochondria should be investigated polarografically along with histology and histochemistry. Finally several parts of the respiratory chain and pyruvate dehydrogenase complex are analyzed by single enzyme measurement. Also combined deficiencies have been described. Polypeptide subunits of respiratory chain complexes can be investigated by means of immunoblotting. The investigations of the mitochondrial DNA from the end of the diagnostic scale. The application of various new therapeutic agents, such as antioxidants, radical scavangers and cofactors have not come to any persuasive clinical result. But there is a number of reports about some successful treatment with coenzyme Q10, vitamin K3, vitamin C, riboflavin, thiamine, dichloroacetate and in PDHC -deficiency with ketogenic diet. Mitochondrial gene therapy appears only theoretical and speculative. Because of the enormous heterogeneity even on the DNA-level genetic counselling is reserved for some cases with exact molecular diagnosis.