Among the 92 patients who presented with high GGT activity cholestasis, 55 were diagnosed with Alagille syndrome, bearing either a JAG1 mutation (n = 48) or a NOTCH2 mutation (n = 7), 17 patients were diagnosed with PFIC3, nine with neonatal sclerosing cholangitis related to DCDC2 deficiency, three with cystic fibrosis, three with Wilson disease and five with alpha one anti-trypsin (A1AT) deficiency. The gene discussed is DCDC2; the disease is cystic fibrosis.