Clinical relapse of immune‐mediated thrombotic thrombocytopenic purpura following COVID‐19 vaccination

De novo and relapsed immune‐mediated thrombotic thrombocytopenic purpura (iTTP) have been documented to have occurred following severe acute respiratory syndrome coronavirus 2 (COVID‐19) vaccination. Here, we present a case of a 28‐year‐old woman who received the tozinameran (BNT162b2, Pfizer‐BioNtech) vaccine for COVID‐19 and experienced an iTTP relapse during longitudinal follow‐up. She received the vaccine 30 months after her initial diagnosis, while she was in clinical remission. She was not in complete ADAMTS‐13 remission, as she had undetectable ADAMTS‐13 activity during follow‐up except for one isolated measurement of 48%. Shortly after vaccination, she developed complaints of bruising, petechiae, ataxia, and an episode of slurred speech. Laboratory testing demonstrated thrombocytopenia, schistocytes, and eventually undetectable ADAMTS‐13 activity. She was successfully treated with caplacizumab, rituximab, and corticosteroids without plasma exchange. She achieved complete clinical and ADAMTS‐13 remission after treatment. We recommend caution in the administration of COVID‐19 vaccines for survivors of iTTP in remission with severely deficient ADAMTS‐13 activity.