GAST and pneumocystosis: This observational study revealed three important findings, namely, (1) the prevalence of WS was higher in patients who used an A-SA, (2) the WS-positive group had a significantly greater prevalence of a high serum gastrin level and a higher percentage of P-CAB users than the WS-negative group, and (3) histopathological examination confirmed a high prevalence of PCP and PCV in biopsy samples of WS.