Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare, autosomal recessive disorder caused by mutations in the TYMP gene, leading to deficiencies in the enzyme thymidine phosphorylase. This results in mitochondrial dysfunction, primarily affecting the gastrointestinal and nervous systems, manifesting as symptoms like gastrointestinal dysmotility, peripheral neuropathy, and leukoencephalopathy.