Severe immunotherapy-related autoimmune hemolytic anemia induced by toripalimab in a patient with deficient mismatch repair colorectal cancer: a case report and literature review

Immune checkpoint inhibitors (ICIs) have recently emerged as a promising class of anticancer therapy, demonstrating significant efficacy across various malignancies. They are currently regarded as the first-line therapy for advanced mismatch repair-deficiency colorectal cancer. However, the extensive clinical usage of ICIs has raised concerns regarding immune-related adverse events (irAEs). Herein, we describe a case of immunotherapy-related autoimmune hemolytic anemia (irAIHA) in a patient with locally advanced mismatch repair-deficiency colorectal cancer treated with toripalimab, a programmed cell death 1 (PD-1) (ICI). The patient developed grade 4 irAIHA after the first cycle of immunotherapy, which was promptly managed by discontinuing treatment and initiating high-dose prednisone. Symptoms were controlled, and hemoglobin returned to normal without resuming immunotherapy. Although hematologic irAEs such as irAIHA are relatively rare, they can be life-threatening and require immediate intervention. This case underscores the importance of vigilant monitoring, early recognition, and timely, aggressive management of irAEs during ICI therapy. In high-risk populations, including elderly patients with comorbidities, the toxicities associated with corticosteroid therapy pose additional challenges, emphasizing the need for individualized strategies that balance efficacy and safety.