Notes: 2-Hydroxyadipic acid is a dicarboxylic fatty acid. Levels of 2-hydroxyadipic acid are decreased in tumor tissue from patients with esophageal squamous cell carcinoma.{68016} Urinary 2-hydroxyadipic acid levels are increased in patients with 2-ketoadipic aciduria, a disorder characterized by a deficiency in lysine, hydroxylysine, and tryptophan degradation.{68017}