Immune Effector Cell-Associated Hemophagocytic Lymphohistiocytosis-Like Syndrome

**Semantic type:** Disease or Syndrome

**Definition:** A group of rare but severe toxicities resembling hemophagocytic lymphohistiocytosis (HLH) that present in a subset of patients with cytokine release syndrome (CRS) following the administration of immunotherapeutic agents, including chimeric antigen receptor (CAR) T-cell preparations. Characteristic findings may include hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, coagulopathy, hepatic transaminitis, hyperbilirubinemia, neutropenia, elevated lactate dehydrogenase, and occasionally hemophagocytosis.

**Synonyms:** - CAR T-cell-Associated HLH - CAR T-cell-Associated Hemophagocytic Lymphohistiocytosis - CAR T-cell-Related HLH-like Syndrome - CAR T-cell-Related Hemophagocytic Lymphohistiocytosis-like Syndrome - CAR T-cell-Related Hemophagocytic Lymphohistiocytosis-like Syndrome - IEC-HS - carHLH