Mutations in the TYMP gene, which encodes the enzyme thymidine phosphorylase, can lead to mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), a rare autosomal recessive disorder characterized by gastrointestinal dysmotility, peripheral neuropathy, and leukoencephalopathy. These mutations result in the accumulation of thymidine and deoxyuridine, which disrupts mitochondrial DNA replication and repair, causing the clinical manifestations of the disease.