Internal medicine

Cell

Hemophagocytic lymphohistiocytosis

Disease

Biology

Cell therapy

Immunology

T cell

Toxicity

Chimeric antigen receptor

Genetics

Medicine

Immune system

British Journal of Haematology

Summary Chimeric antigen receptor T‐cell (CAR T‐cell) therapy is associated with significant toxicities secondary to immune activation, including a rare but increasingly recognised severe toxicity resembling haemophagocytic lymphohistiocytosis (carHLH). We report the development of carHLH in 14·8% of paediatric patients and young adults treated with CD19‐specific CAR T‐cell therapy with carHLH, occurring most commonly in those with high disease burden. The diagnosis and treatment of carHLH required a high index of suspicion and included multidrug immunomodulation with variable response to therapies. Compared to patients without carHLH, patients with carHLH had both reduced response to CAR T‐cell therapy ( P ‐value = 0·018) and overall survival ( P ‐value = &lt; 0·0001).

Hemophagocytic lymphohistiocytosis‐like toxicity (carHLH) after CD19‐specific CAR T‐cell therapy