Abatacept is a fusion protein that blocks T cell activation. It is used in a variety of conditions including organ transplantation, immune deficiency, and autoimmune diseases. Even though abatacept-induced adverse events are observed, hypersensitivity reactions are rare. Desensitization protocols that can be implemented in the case of hypersensitivity reactions are present in the literature for many biological agents. However, a desensitization protocol for abatacept has not yet been established.

Our patient, who was started on one of the biological agents, abatacept, for rheumatoid arthritis due to insufficient response to diseasemodifying antirheumatic drugs, developed immediate hypersensitivity reaction with the first dose. Since it was planned to continue the treatment, abatacept desensitization was performed. The rapid desensitization protocol performed with prior premedication was successful and the patient was able to receive subsequent doses of abatacept using the same protocol.