Drug Reaction With Eosinophilia and Systemic Symptoms (DRESS) Following Conversion Surgery for Esophageal Cancer: A Case Report.

Conversion surgery is increasingly used for initially unresectable esophageal cancer patients responding to induction therapy. The integration of immune checkpoint inhibitors (ICIs) into standard chemotherapy regimens is expected to increase the number of patients undergoing this approach. However, ICIs can cause immune-related adverse events (irAEs), which are often difficult to diagnose in the postoperative setting. Among these, drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome is a rare but potentially life-threatening complication. A 71-year-old woman with stage IVA esophageal squamous cell carcinoma received induction chemotherapy, including nivolumab, fluorouracil, and cisplatin, followed by successful conversion surgery. Postoperatively, she developed fever, widespread rash, eosinophilia, and liver dysfunction. Initial suspicion was sepsis, and broad-spectrum antibiotics were started. However, repeated tests showed no infection. The retrospective review met the criteria for DRESS syndrome, with the postoperative contrast agent likely triggering the reaction. Supportive care and discontinuation of unnecessary antibiotics led to gradual improvement, and she was discharged for rehabilitation. This case highlights the diagnostic challenge of hypersensitivity reactions such as DRESS in the postoperative setting after ICI-based therapy. Although not a classical irAE, ICI-induced immune dysregulation may have contributed to its development. Awareness of atypical irAEs is essential for timely diagnosis and appropriate management.