Less frequent complications following CAR T-cell therapies: hemophagocytic lymphohistiocytosis, graft-versus-host disease, thrombotic microangiopathy, coagulation disorders and secondary malignancies: best practice recommendations from the EBMT Practice Harmonization and Guidelines Committee.

CAR T-cell therapies have revolutionized the treatment of hematologic malignancies; however, alongside the well-known complications of cytokine release syndrome (CRS), neurotoxicity, immune effector cell-associated hematotoxicity (ICAHT), and infections, other non-classical toxicities are emerging. This review, developed by the EBMT Practice Harmonization and Guidelines Committee, addresses the management of other critical post-CAR T-cell complications including hemophagocytic lymphohistiocytosis (HLH), graft-versus-host disease (GvHD), thrombotic microangiopathy (TMA), coagulation disorders and secondary malignancies. These complications, though less frequent, present a significant challenge, often contributing to morbidity and mortality with no standardized management protocols. This review provides best practice recommendations for early identification, risk mitigation, and therapeutic interventions, supported by limited but emerging clinical evidence. Comprehensive expert guidance is essential for optimal management of these under-explored toxicities following CAR T-cell therapies.