Sintilimab-associated hemophagocytic lymphohistiocytosis: a case report

Hemophagocytic lymphohistiocytosis (HLH) is a rare hematologic syndrome characterized by massive, uncontrolled cytokine release, which can lead to multiple organ failure and is associated with a high mortality rate. Recent studies have found that checkpoint inhibitors (ICIs) can induce HLH. This case report describes a 75-year-old man with metastatic esophageal squamous cell carcinoma (ESCC) who developed sintilimab-associated HLH, presenting as refractory fever and respiratory symptoms initially misdiagnosed as infection. The diagnosis, confirmed via elevated ferritin, sCD25, and reduced NK-cell activity, was delayed due to nonspecific symptoms. Following the initiation of dexamethasone, the patient's symptoms resolved and laboratory parameters normalized, leading to complete remission. The case highlights HLH as a rare but life-threatening immune-related adverse event of checkpoint inhibitors, underscores the importance of early multidisciplinary discussion (MDT) in patients with unexplained fever, and demonstrates the early diagnosis and treatment are critical.