A well-established example in gliomas is isocitrate dehydrogenase (IDH) (Yan et al., 2009), which converts isocitrate to α-KG, mutations have also been found in succinate dehydrogenase (SDH) and fumarate hydratase (FH) in other conditions including phaeochromocytoma, paraganglioma, and renal cell carcinoma (Eng et al., 2003). Here, FH is linked to paraganglioma.