MDH2 and hereditary pheochromocytoma-paraganglioma: Pheochromocytomas and paragangliomas (PPGLs) are tumors of the adrenal medulla and autonomic ganglia, respectively, that often demonstrate this HIF-dependent pseudohypoxic switch of energy metabolism, in particular when associated with specific hereditary syndromes including Von Hippel-Lindau (VHL), SDHA, SDHB, SDHC, SDHD, SDHAF2, Egl nine homolog 1 (EGLN1/PHD2), EGLN2(PHD1), malate dehydrogenase 2 (MDH2), and fumarate hydratase (FH) (Dahia et al. 2005, Robledo et al. 2017).