CEAS/CNSU caused by SLCO2A1 defects, as well as congenital/familial diarrhea associated with SLC26A1, SLC9A3, and GUCY2C mutations, were the most prevalent monogenic disorders in patients with LO-mIBD, significantly more common than in those with IO-mIBD (p < 0.001, Table 4). The gene discussed is GUCY2C; the disease is Diarrhea.