We demonstrated that the presence of basal plasmacytosis predicts UC clinical relapse in patients with complete mucosal healing. We recommend closer follow-up and optimization of medical therapy in patients with basal plasmacytosis.

Objective Lymphocyte recruitment to the inflamed gut is increased in UC. Inhibition of this cell trafficking by vedolizumab (VDZ) was successful in inducing and maintaining remission and in induction of endoscopic mucosal healing. There are no data on histological healing with VDZ. We studied histological changes following VDZ therapy and compared gene expression in patients with UC before and after therapy. Design Forty-one patients with UC from GEMINI I and LTS were studied before and at three time points (weeks 6/12/52) following VDZ therapy. Colonic biopsies were scored using the Geboes index and correlated with Mayo endoscopic subscore. Gene expression was analysed using Affymetrix gene arrays. Results Fifty-five per cent of patients achieving endoscopic healing (= Mayo endoscopic subscore 0-1) with VDZ at the studied time points also had histological healing (= Geboes grade 0-1). In most healers, some residual histological changes (eg, disturbed architecture and increased mononuclear cell infiltrate) were still observed, although this was less at week 52. VDZ restored expression of many inflammatory genes in patients with endoscopic healing only at week 52 and not before. In VDZ healers, the expression of many genes remained dysregulated at weeks 6/12/52 compared with controls. Conclusions VDZ induces histological healing in >50% of patients with endoscopic healing, with maximal effect at week 52. VDZ also restored, although incompletely, the colonic expression of many immunerelated genes in patients with UC achieving endoscopic healing at week 52. However, persistent histological and gene dysregulations did remain even in healers, suggesting that maintenance therapy will be necessary to control the intestinal inflammation. Trial registration numbers: NCT00783718 and NCT00790933; post-results.

Both extremes of the histologic and endoscopic activity scores neatly correlate, but important misclassifications exist for mild disease. Microscopy may detect more severe disease than endoscopically suspected, possibly altering the clinical follow-up scheme. We also infer from our results that histologic scoring should be used in addition to endoscopy when scoring disease activity for clinical trials.

One hundred and seventy-one UC patients (38% female, median age 47 years, median disease duration 13 years) were included. The MMES correlated significantly with the PMS (r = 0.535), CRP (r = 0.238), FC (r = 0.730) and GS (r = 0.615) (all p < 0.001). Median MMES scores were significantly higher in patients with clinical, biological or histological activity (all p ≤ 0.001) CONCLUSIONS: The MMES is an easy to use endoscopic index for UC that combines the severity analysis of the MES with disease extent, and correlates very well with clinical, biological and histological disease activity.

The assessments of histological activity based on the OGS and the SGS were comparable in newly diagnosed active UC patients. Further prospective validation should now be done to replace the OGS with the SGS.