TYMP and mitochondrial neurogastrointestinal encephalomyopathy: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE, Online Mendelian inheritance in Man #603041, Genome Database accession #9835128) is an ultra-rare autosomal recessive disease caused by mutations in TYMP, the nuclear gene which encodes for the enzyme, thymidine phosphorylase.