We previously described that gastric achlorhydria was mediated by a mutation in the ATPase H+/K+ transporting alpha subunit (ATP4A) gene (patient F1, see Table 1), which encodes the proton pump expressed in parietal cells (PCs) responsible for gastric acidification, and correlates with chronic gastritis that leads to gNETs [11,12]. The gene discussed is ATP4A; the disease is chronic gastritis.