TYMP and mitochondrial neurogastrointestinal encephalomyopathy: Perhaps the most promising potential disease-modifying therapy for a congenital mitochondrial disorder currently in clinical use is allogeneic hematopoietic stem cell transplantation (AHSCT) for children with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), an extremely rare mitochondriopathy caused by mutations in the TYMP gene.