OTC and Hyperammonemia: Although suspected in few additional patients (hyperammonemia with high urinary orotic acid expected in OTC deficiency), there was insufficient evidence to prove OTC deficiency in some patients because of the difficulty in performing enzyme based diagnosis (which would have required a liver biopsy) or due to lack of mutations in the OTC gene despite full gene study (sequencing as well as testing for larger deletions and duplications by MLPA).