The impaired function of another enzyme in the Krebs cycle, called succinate dehydrogenase, also leads to pseudohypoxia, because of the accumulation of succinate, and the causative inhibition of propyl hydroxylase, the enzyme which hydroxylate HIF1A and HIF2A (the name of the associated tumor syndrome is Hereditary Pheochromocytoma and/or Paraganglioma). This evidence concerns the gene HIF1A and neoplastic syndrome.