Acute post-exercise rhabdomyolysis may result in the muscle-pain in combination with muscle-weakness, dark coloured urine due to myoglobinuria, and elevated serum levels of aminotransferases, creatine kinase, and myoglobin. A heterogeneous group of acquired or inherited diseases can cause these symptoms. Extreme myoglobinuria is associated with the risk of development of acute renal failure. We describe clinical manifestation and results of biochemical and molecular analyses in two young men with acute rhabdomyolysis caused by mitochondrial disorders of beta oxidation of fatty acids. In a 20year old patient after attack of rhabdomyolysis the VLCAD (very long-chain Acyl-Co A dehydrogenase deficiency) was diagnosed and in a 10year old boy the LCHAD (long-chain 3-OH-Acyl-CoA dehydrogenase deficiency) was revealed. Early confirmation of these mitochondrial disorders made effective the-rapy possible.

        Key words: rhabdomyolysis, metabolic myopathy, exercise-induced myoglobinuria, disorders of beta-oxidation of fatty acids, LCHAD, VLCAD.