A substantial proportion of patients with autoimmune diseases experienced a new side effect called local immune effector cell–associated toxicity syndromes (LICATS) after receiving chimeric antigen receptor (CAR) T-cell therapy; these effects were usually mild, self-limited, and occurred in organs previously affected by the autoimmune condition.

• The severity of events of LICATS was mostly mild (grade 1, 65%), with only three patients requiring prolonged or new hospitalization. All events of LICATS occurred during B-cell aplasia and in organs previously affected by the autoimmune disease.
• The most common manifestations of LICATS were transient skin rashes (35%), a worsening of kidney function or proteinuria (22%), and musculoskeletal symptoms (19%).

“LICATS typically occurred during the period of time when CAR T cells peaked, suggesting an immunological basis for this clinical phenomenon. This distinction has important implications, as clinicians might want to escalate immunosuppression for patients in whom a flare is suspected. Increased education and awareness of LICATS could avert unnecessary use of added immunosuppression following CAR T-cell infusions,” experts wrote in an accompanying editorial.

This study was led by Melanie Hagen, MD, Friedrich-Alexander-Universität Erlangen-Nürnberg and Universitätsklinikum Erlangen, Erlangen, Germany. It was published online on April 30, 2025, in The Lancet Rheumatology.

In this study, only a limited number of biopsies were taken from the skin, gastrointestinal tract, and kidneys, potentially restricting a comprehensive understanding of the tissue-specific effects of LICATS. The absence of a comparator group is another major drawback of this study.

This study received funding from Deutsche Forschungsgemeinschaft, German Cancer Aid, Bundesministerium für Bildung und Forschung, and other sources. Some authors reported receiving grants, honoraria, consultancy fees, support for attending meetings, and other ties from various pharmaceutical companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.