SDHD and neoplasm: Since the original discovery of SDHD mutations in hereditary PGL in 2000, the genes encoding all four proteins that constitute the succinate dehydrogenase (SDH) complex as well as the required assembly factor (SDH assembly factor 2: SDHAF2) have been shown as tumour-suppressor genes in familial and apparently sporadic PCC and PGL1, 2, 3, 4, 5.