Abstract
Treatments using immune checkpoint inhibitors such as pembrolizumab lead to immune mediated adverse effects including hemophagocytic lymphohistiocytosis (HLH). Herein, we present a case where HLH developed after pembrolizumab administration, which was treated using high dose prednisolone. He developed high-grade fever complicated with liver dysfunction and diarrhea 7 days after pembrolizumab administration. Although treatment with oral prednisolone alleviated the symptoms, other adverse effects arose owing to a tapered prednisolone dose. Hyperferritinemia suggested the diagnosis of HLH and met the criteria for HLH diagnosis. He was thus administered intravenous pulses of methylprednisolone followed by high-dose oral prednisolone, which resolved these symptoms.