The co-occurrence of multiple deletions, depletion, and somatic mtDNA point mutations was often described in muscle of MNGIE patients, as a consequence of mitochondrial dNTP imbalance due to TP deficiency (Hirano et al., 1994; Nishigaki et al., 2003). Here, TYMP is linked to mitochondrial neurogastrointestinal encephalomyopathy.