Hereditary thrombotic thrombocytopenic purpura and COVID‐19: Impacts of vaccination and infection in this rare disease

INTRODUCTION: Severe COVID‐19 is associated with an important increase of von Willebrand factor and mild lowering of ADAMTS13 activity that may, in the presence of a strong inflammatory reaction, increase the risk of acute thrombotic thrombocytopenic purpura (TTP). Although acute episodes of immune‐mediated TTP associated with COVID‐19 or SARS‐CoV‐2 vaccination have been reported, data about clinical evolution of hereditary TTP (hTTP) during the pandemic are scarce. METHOD: We conducted a survey among adult patients of the International Hereditary TTP Registry about SARS‐CoV‐2 vaccination, COVID‐19, and occurrence of acute hTTP episodes. RESULTS: Of 122 adult hTTP patients invited to participate, 86 (70.5%) responded. Sixty‐five had been vaccinated (75.6%), of which 14 had received in addition a booster, resulting in 139 individual vaccine shots. Although vaccinations in patients on plasma prophylaxis were done within 1 week of the last plasma infusion, all 23 patients treated with plasma on demand were vaccinated without prior plasma infusions. One patient on uninterrupted weekly plasma infusions presented within 3 days from his second vaccination with neurological symptoms and computed tomography scan 9 days later showed subacute ischemic/hemorrhagic frontal lobe infarction. A second male patient developed acute myocarditis after his second dose of mRNA‐1273 vaccine. Twelve (14%) patients had COVID‐19, associated with an acute hTTP episode in three of them: one patient had a transient ischemic attack, one a stroke, and a pregnant woman was hospitalized to intensify plasma treatment. DISCUSSION: The risk of an acute episode triggered by COVID‐19 seems higher than following vaccination in hTTP patients, who can be safely vaccinated against SARS‐CoV‐2.