Enhancer of Zeste Homolog 1 and 2 Inhibitor-induced Colitis Mimicking Immune Checkpoint Inhibitor-induced Colitis.
Keisuke Iwata, Kenji Yamazaki, Ryoji Kushima et al.
✦ AI-curated · Sources linked
Case in brief
An 80-year-old woman with relapsed nodal T-follicular helper cell lymphoma developed severe watery diarrhea while receiving valemetostat, an EZH1/2 inhibitor. Colonoscopy showed diffuse mucosal erythema and edema. Biopsy demonstrated lymphoplasmacytic infiltration, crypt abscesses, and apoptotic bodies, with CD3-positive T cells predominating and abundant CD8-positive cells. The findings resembled immune checkpoint inhibitor-induced colitis. Her diarrhea improved after valemetostat was discontinued, without additional treatment.
What made this case unusual
The colitis associated with EZH1/2 inhibitor therapy mimicked immune checkpoint inhibitor-induced colitis clinically and histologically, raising a diagnostic consideration beyond the drug class more commonly linked to this pattern.
Diagnostic / clinical pearl
In a patient receiving an EZH1/2 inhibitor who develops persistent diarrhea, consider drug-associated colitis; endoscopic and histological assessment can help characterize the injury.