Autoimmune gastritis: long-term natural history in naïveHelicobacter pylori-negative patients

Autoimmune gastritis (AIG) is an immunomediated disease targeting parietal cells, eventually resulting in oxyntic-restricted atrophy. This long-term follow-up study aimed at elucidating the natural history, histological phenotype(s), and associated cancer risk of patients with AIG consistently tested H. pylori-negative (naïve H. pylori-negative subjects).Two-hundred eleven naïve H. pylori-negative patients (tested by serology, histology, molecular biology) with AIG (F:M=3.15:1; p<0.001) were prospectively followed up with paired biopsies (T1 vs T2; mean follow-up years:7.5 (SD:4.4); median:7). Histology distinguished non-atrophic versus atrophic AIG. Atrophy was further subtyped/scored as non-metaplastic versus metaplastic (pseudopyloric (PPM) and intestinal (IM)). Enterochromaffin-like-cell (ECL) status was categorised as diffuse versus adenomatoid hyperplasia/dysplasia, and type 1 neuroendocrine tumours (Type1-NETs).Over the long-term histological follow-up, AIG consistently featured oxyntic-predominant-mononuclear inflammation. At T1, PPM-score was greater than IM (200/211 vs 160/211, respectively); IM scores increased from T1 to T2 (160/211 to 179/211), with no changes in the PPM prevalence (T1=200/211; T2=201/211). At both T1/T2, the prevalence of OLGA-III-stage was <5%; no Operative Link on Gastritis Assessment (OLGA)-IV-stage occurred. ECL-cell-status progressed from diffuse to adenomatoid hyperplasia/dysplasia (T1=167/14 vs T2=151/25). Type1-NETs (T1=10; T2=11) always coexisted with extensive oxyntic-atrophy, and ECL adenomatoid-hyperplasia/dysplasia. No excess risk of gastric or other malignancies was found over a cumulative follow-up time of 10 541 person years, except for (marginally significant) thyroid cancer (SIR=3.09; 95% CI 1.001 to 7.20).Oxyntic-restricted inflammation, PPM (more than IM), and ECL-cell hyperplasia/neoplasia are the histological AIG hallmarks. Compared with the general population, corpus-restricted inflammation/atrophy does not increase the GC risk. The excess of GC risk reported in patients with AIG could plausibly result from unrecognised previous/current H. pylori comorbidity.