A novel TYMP mutation in a French Canadian patient with mitochondrial neurogastrointestinal encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disorder characterized by gastrointestinal, extraocular muscle, peripheral nerve, and cerebral white matter involvement. Mutations in the nuclear gene TYMP encoding for thymidine phosphorylase (TP) cause loss of TP activity, systemic accumulation of its substrates in plasma and tissues, as well as alterations in mitochondrial DNA including deletions, depletion, and somatic point mutations. To date, more than 30 mutations have been reported in diverse ethnic populations. We present herein the clinical, neuroimaging, neuromuscular, and molecular findings of the first French Canadian patient with MNGIE caused by a novel homozygous invariant splicing site (IVS5 +1 G>A) mutation of the TYMP gene.