Haemophagocytic lymphohistiocytosis (HLH) that occurs concomitantly with leukaemia can be initially missed due to overlapping clinical features. In a series of three cases, Tanabe and colleagues illustrate the need for prompt recognition of HLH and institution of HLH‐directed therapy to prevent hyperinflammation‐mediated multi‐organ damage and death.Commentary on: Tanabe et al. Paediatric acute lymphoblastic leukaemia‐associated haemophagocytic lymphohistiocytosis develops during prednisolone prephase. Br J Haematol 2024; 205:2031‐2035.