Treatment of Rituximab-induced Crohn's Disease With Ustekinumab Induction and Long-term Maintenance of Remission

The Possible Pathogenic Role of IgG4-Producing Plasmablasts in Stricturing Crohn's Disease

BACKGROUND

Crohn's disease (CD) is a condition on the spectrum of inflammatory bowel disease that affects up to 20 people per 100,000 in the US annually, and with incidence increasing. One of the most significant sources of morbidity in CD is the formation of strictures, with resultant intestinal blockage a common indication for hospitalization and surgical intervention in these patients. The pathophysiology of stricture formation is not fully understood. However, the fibroplasia that leads to fibrostenotic stricture formation may have shared pathophysiology with IgG4-related fibrosis.

SUMMARY

Initial intestinal inflammation recruits innate immune cells, such as neutrophils, that secrete IL-1β and IL-23, which induces a type 17 CD4+ T-helper T-cell (Th17)-mediated adaptive immune response. These CD4+ Th17 T cells also contribute to inflammation by secreting proinflammatory cytokines such as IL-17 and IL-21. IL-21 recruits and stimulates CD4+ T follicular helper (Tfh) cells, which secrete more IL-21. This causes ectopic germinal center formation, recruiting and stimulating naïve B cells. The IL-17 and IL-21 produced by Th17 cells and Tfh cells also induce IgG4 plasmablast differentiation. Finally, these IgG4-producing plasmablasts secrete platelet-derived growth factor (PDGF), which activates local PDGF-receptor expressing fibroblasts and myofibroblasts, resulting in uncontrolled fibroplasia.

Rituximab-induced Ileocolitis in a Patient with Gastric MALToma: A Case Report and Literature Review

Rituximab (RTX) is effective for treating cancer, but reports of RTX-associated enterocolitis are limited. We herein report the case of a 65-year-old man who developed RTX-induced ileocolitis. He was diagnosed with gastric mucosa-associated lymphoid tissue lymphoma (MALToma) and treated with RTX. He complained of bloody diarrhea after RTX. Mucosal inflammation on colonoscopy indicated RTX-induced ileocolitis. He was treated with corticosteroids, and his symptoms improved. We reviewed the RTX-associated gastrointestinal adverse events and classified the features into ulcerative colitis, Crohn's disease, microscopic colitis, and ileocolitis. To our knowledge, this is the first case of a Japanese patient who developed RTX-induced ileocolitis.