Fumarate hydratase (FH) or succinate dehydrogenase (SDH) loss-of-function mutations lead to a buildup of fumarate or succinate, respectively, and are found in paragangliomas, pheochromocytomas, leiomyomatosis, and renal cell cancer (Favier et al. 2015, Yong et al. 2020). The gene discussed is FH; the disease is paraganglioma.