2-Methylsuccinic acid (Pyrotartaric Acid) is a normal metabolite found in human fluids. Increased urinary levels of 2-Methylsuccinic acid (Pyrotartaric Acid) (together with ethylmalonic acid) are the main biochemical measurable features in ethylmalonic encephalopathy, a rare metabolic disorder with an autosomal recessive mode of inheritance that is clinically characterized by neuromotor delay, hyperlactic acidemia, recurrent petechiae, orthostatic acrocyanosis, and chronic diarrhea.