Mild-to-moderate psoriasis is associated with subclinical inflammation in the duodenum and a tendency of disturbed intestinal barrier

Psoriasis is a chronic skin disease occasionally associated with abdominal symptoms and IBD. We aimed to characterize intestinal immune cells and the integrity of the intestinal barrier in psoriasis. Biopsies from the duodenum and colon were analyzed by flow cytometry and immunohistochemistry for the presence and activation status of different immune cell populations. Intestinal permeability was measured using Ussing chambers. Proinflammatory markers were analyzed in fecal and blood samples using ELISA. The intestinal level of inflammatory mediators was assessed using a multiplex proximity extension assay. We found an increased density of intestinal eosinophils, mast cells, macrophages, and CD8⁺ T-cells in psoriasis; eosinophils, macrophages, and CD8+ T-cells expressed activation markers. Half of the psoriasis patients showed increased permeability across the duodenum, correlating with increased mucosal IL-17A, IL-13, IL-2, and IL-20, and with gastrointestinal symptoms. Our findings reveal that psoriasis is associated with low-grade intestinal inflammation, which may contribute to abdominal symptoms in these patients and possibly set the stage for the development of intestinal disease.