In the last ten years, it is emerging that the metabolic reprogramming of cancer cells and mutations in metabolic enzymes, such as fumarate hydratase (FH), succinate dehydrogenase (SDH), and isocitrate dehydrogenase (IDH), cause the accumulation of particular intermediary metabolites with a driving role in cancer initiation and maintenance. The gene discussed is IDH3A; the disease is cancer.