Severe bloody diarrhea due to cytokine release syndrome after chimeric antigen receptor T cell therapy for refractory acute lymphoblastic leukemia

Cytokine release syndrome (CRS), which may be associated with fever, hypotension, hypoxia, and organ damage, is caused by a massive cytokine release after chimeric antigen receptor (CAR)-T cell therapy. We present the case of a patient who developed severe bloody diarrhea due to CRS after CAR-T cell infusion. A 10-year-old boy presented with a second relapse of B-cell precursor acute lymphoblastic leukemia 6 months after hematopoietic stem cell transplantation from an unrelated donor. CAR-T cells (tisagenlecleucel) were infused at the third complete remission after salvage chemotherapy. While fever >39°C was sustained from day 4, circulatory and respiratory status remained stable. However, he experienced severe bloody diarrhea. There was no evidence of infection; lower gastrointestinal (GI) endoscopy revealed extensive edema with erosion and ulceration, suggestive of non-specific intestinal inflammation. Thus, we considered CRS-associated grade 3 GI damage and administered a single dose of tocilizumab for grade 2 CRS, followed by 4 days of corticosteroids. Afterwards, no fever or GI bleeding was observed. Biopsy of the intestinal mucosa revealed ulcerative change with a lack of epithelial cells, which may correspond to histologic grade 4 graft versus host disease (GVHD). However, diarrhea corresponded to stage 1 GVHD, and the GVHD risk after CAR-T cell infusion has been reported to be rare in clinical practice. Although severe GI symptoms associated with CRS after CAR-T therapy are rare, early tocilizumab use is recommended for non-infectious severe GI symptoms to avoid long-term corticosteroid use, which may reduce CAR-T cell efficacy.