FUT2 and attention deficit-hyperactivity disorder: Interestingly, the 19q13.33 locus, which was identified as pleiotropic loci for 2 pairs of traits, was only colocalized between PUD and schizophrenia (PP.H4 = 0.8927) rather than PUD and ADHD (PP.H4 = 0.3552), with the same potential shared causal variant rs681343 identified (mapped gene: FUT2).