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.