Human herpesvirus 6 myelitis after chimeric antigen receptor T-cell therapy.

This article reports a fatal case of human herpesvirus 6 (HHV-6) myelitis following CD19-targeted chimeric antigen receptor T-cell therapy. Infection from HHV-6 reactivation after haematopoietic stem cell transplant is established, and outside of this population is limited to case reports. The patient developed cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome that responded to corticosteroids both clinically and on imaging. Subsequently, ascending flaccid paralysis developed, leading to neuromuscular respiratory failure and, ultimately, death. Disease progression was refractory to foscarnet and multiple immunomodulating agents. HHV-6 should be considered in patients with encephalitis and myelitis after adoptive T-cell therapy.