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Mitochondriopathies - Overview
General Information
Mitochondrial Diseases:
Differential genetic diagnostics according to clinical features, morphology and biochemistry
Mitochondrial defects lead to cellular metabolic failure and play an important role in pediatrics and neurology, where the prevalence of mitochondrial diseases is still difficult to determine. Many different organs can be affected, most often the brain, muscles, liver and heart with variable clinical manifestations, which makes targeted testing difficult.
The genetic causes of mitochondrial malfunction are mutations in nuclear coded genes or in mitochondrial DNA (mtDNA), the latter of which inherited only from the mother.
In testing for mitochondriopathies one need to take into account not only clinical manifestations, but morphology, biochemistry and genetic abnormalities as well. It is not necessary that all mutations be found in all tissues in order to pursue testing. Some clinical diagnoses (e.g. LHON, Alpers Syndrome, SANDO, autosomal dominant PEO, autosomal dominant Opticus Atrophy) can be cleared up by molecular genetic testing of a patient's blood DNA; common clinical manifestations may allow for targeted genetic testing of blood DNA (e.g. POLG1, DGUOK, SURF1, SUCLA2) based on specific clinical features. If test results are negative, targeted genetic diagnostics are only possible with the help of histological, biochemical and molecular genetic testing of muscle tissue (or, in some cases, skin fibroblasts).
The number of potential disease-inducing gene mutations is increasing all the time and diagnostic methods are improving rapidly; it is thus necessary to continually advance and adjust the diagnostic process. However there are still numerous patients and families affected by mitochondriopathies for whom no genetic defect has been found. Additional functional testing and linkage analysis can be of help to families with suitable anamnesis. In such cases, close cooperation between various specialists and laboratories is indispensable.