Immune checkpoint inhibitor-associated hemophagocytic lymphohistiocytosis in a patient with chronic lymphocytic leukemia.

Haemophagocytic lymphohistiocytosis (HLH) is a rare complication of immune checkpoint inhibitor therapy. A 55-year-old male with stable chronic lymphocytic leukemia presented with fevers and symptomatic anaemia after nine cycles of nivolumab for metastatic melanoma. Investigations were consistent with autoimmune haemolytic anemia and corticosteroids were initiated. Thrombocytopenia and elevated liver enzymes without evidence of chronic lymphocytic leukaemia transformation was present. Ferritin was elevated, and thus HLH was considered and subsequently confirmed on a bone marrow biopsy. Corticosteroid monotherapy was continued, with resolution of fevers and improvement in cytopenias and liver enzymes. A six month corticosteroid tapering regimen was initiated, and he remains in HLH remission. This case highlights the importance of prompt recognition of immune checkpoint inhibitor-related HLH in patients with concurrent haematological malignancy.