Mitochondrial complex II (succinate:ubiquinone oxidoreductase) is the smallest complex of the system for oxidative phosphorylation (OXPHOS) consisting of the four structural subunits SDHA, SDHB, SDHC and SDHD and for assembly factors for complex II are known: SDHAF1-4. Complex II deficiency accounts for approx. 2% of all mitochondrial disorders. Numerous pathogenic SDHA-variants have been reported which describe two broad clinical manifestations, either susceptibility to cancer in the case of single, heterozygous germline variants, or a mitochondrial disease presentation, almost exclusively due to bi-allelic recessive variants and associated with an isolated complex II deficiency manifesting with Leigh-syndrome, leukoencephalopathy, cardiomyopathy and optic atrophy.
SDHA