Deoxyuridine accumulation in urine in thymidine phosphorylase deficiency (MNGIE)

We report the presence of the unusual nucleoside deoxyuridine in the urine of a patient with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) (MIM 603041) due to thymidine phosphorylase (TP:EC 2.4.2.4) deficiency. Thymidine, uracil and thymine were also elevated. We propose that inhibition of thymidylate synthetase by TMP leads to the accumulation of dUMP which may be degraded to deoxyuridine or metabolised to dUTP. Incorporation of dUTP into mtDNA may explain the multiple deletions characteristic of TP deficiency.