TYMP and mitochondrial neurogastrointestinal encephalomyopathy: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE, MIM: 603041) is a ultra‐rare, progressive autosomal recessive metabolic disorder caused by mutations in the nuclear gene TYMP (OMIM: 131222), which codes the enzyme thymidine phosphorylase (TP, EC: 2.4.2.4).1