Association between mucus phenotypes, histopathological features, and ultra-high magnification endoscopic findings in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease affecting the colonic mucosa. Changes in mucin phenotype may be associated with mucosal inflammation in UC. However, the relationship between clinicopathological features and mucus phenotypes in UC remains unclear. Therefore, we aimed to evaluate the association between mucus phenotypes and clinicopathological features in patients with UC using immunohistochemistry, as well as their association with ultra-high magnification endocytoscopy (EC) classification. A total of 51 lower gastrointestinal endocytoscopy procedures were performed for 39 patients with UC between 2018 and 2022. MUC2 expression was positive in all biopsy specimens, whereas MUC1, MUC6, and CD10 expression was negative. MUC5AC was expressed in 51.3% of cases. MUC5AC positivity was associated with duration of disease, classification by clinical course, Mayo score, Mayo endoscopic subscore (MES), Nancy histological index, C-reactive protein levels, erythrocyte sedimentation rate, and EC classification at the patient level. At the specimen level, significant differences were observed in the Nancy histological index, MES, and EC classification. In multivariate analysis, the Nancy histological index showed a significant correlation.MUC5AC is strongly correlated with histopathological severity and may also be associated with clinical and endoscopic severity. The clinical significance of MUC5AC positivity remains a topic for future investigation.