Clinical Approach to the Diagnosis of Mitochondrial Disease

Mitochondrial diseases are primary disorders of the mitochondrial respiratory chain. They are caused by known or presumed genetic mutations in mitochondrial or nuclear genes encoding subunits of the respiratory chain or a number of nuclear genes required for: import of respiratory chain subunits into mitochondria; assembly of functional respiratory chain complexes; replication, transcription and translation of mitochondrial DNA. This complexity is reflected in the different inheritance patterns of mitochondrial diseases and considerable variability in the clinical presentations throughout life. This chapter summarises the epidemiology and presentation of mitochondrial diseases, the major clinical features and classification schemes and presents a diagnostic approach to patient with a presumed mitochondrial disease.