SDHB and pheochromocytoma: Mutations in other SDH component genes—SDHA,SDHC,SDHD, andSDHAF2—also lead to paragangliomas or phaeochromocytomas or both; however, malignancy is rarely associated with these tumours.SDH mutations cause a metabolic imbalance that leads to a DNA and histone hypermethylation phenotype; genes targeted by aberrant methylation are thought to be required for tumour development in these models23.