Ornithine transcarbamylase deficiency, an X-linked disorder, is the most common inherited urea cycle defect. Previous reports have documented the existence of several different mutations that can, partly at least, explain the phenotypic variability of the disorder. We describe the only male with T343K mutation, which also is present in his mother. We underline the disorientation of the beginning of clinical presentation; the patient became ill when fruits were added to his diet.