Molecular biological diagnostics of metabolic myopathies

The group of metabolic myopathies includes glycogen storage diseases, lipid storage diseases and mitochondrial diseases. While diagnostics of glycogen and lipid storage diseases is done biochemically, most mitochondrial disor ders can be diagnosed by genetical characterisation. Mitochondrial disorder s are rare diseases, caused by alterations of the mitochondrial respiratory chain. Most frequently the defects are caused by mutations of the mitochon drial DNA. These can be divided into length variations (deletions, duplicat ions) and DNA point mutations. Mostly they are maternally inherited, but sp oradically appearing diseases are found as well. For the detection of delet ions and duplications, southern blotting is commonly used, while point muta tions are recognized by polymerase chain reaction in daily diagnostics. Cru cial for successful examinations is first to find a reasonable tentative di agnosis and then the choice of the suitable tissue for the assay.