Among the 1307 UCD patients in whom tTG were performed, 1215 resulted negative, while 92 resulted positive: 70/1307 (5.4%) had tTG titre higher than 2 x ULN, and 22/1307 (1.7%) had tTG titre higher than 10 x ULN. This evidence concerns the gene TGM2 and urea cycle disorder.