Original articles Mitochondrial disease heterogeneity: a prognostic challenge

Mitochondrial diseases are a heterogeneous group of progres-sive, genetically transmitted, multisystem disorders caused by impaired mitochondrial function. The disease course for indi-viduals with mitochondrial myopathies varies greatly from pa-tient to patient because disease progression largely depends on the type of disease and on the degree of involvement of various organs which makes the prognosis unpredictable both within the same family and among families with the same mutation. This is particularly, but not exclusively, true for mitochondrial disor-ders caused by mtDNA point mutations, which are maternally inherited and subject to the randomness of the heteroplasmy. For this reason, the prognosis cannot be given by single mitochon-drial disease, but should be formulated by any single mitochon-drial disease-related event or complication keeping in mind that early recognition and treatment of symptoms are crucial for the prognosis. The following approach can help prevent severe organ dysfunctions or at least allow early diagnosis and treatment of disease-related complications. Key words: multisystem disorders, clinical heterogeneity, intrafa-milial variability, dual genetic contro