A Rare Case of Severe Manifestation of COVID-19 Infection Presenting as Immune-Related Thrombotic Thrombocytopenic Purpura With Multiorgan Involvement Treated With Plasmapheresis, Steroids, Rituximab, and Caplacizumab.

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy (TMA) caused by decreased activity of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). Platelet-rich thrombi in small vessels lead to fragmentation of RBCs causing microangiopathic hemolytic anemia (MAHA). Therapeutic plasma exchange is life-saving and is the mainstay of the treatment of TTP. Higher dose IV steroids along with rituximab are used as an adjunct to plasma exchange. Our case report describes a 26-year-old healthy male who presented with new onset seizures and encephalopathy. Blood work demonstrated anemia, severe thrombocytopenia, elevated lactate dehydrogenase, decreased haptoglobin, and elevated creatinine, and peripheral blood smear showed marked schistocytosis indicating MAHA. Plasma exchange and high-dose steroids were started on a presumptive diagnosis of TTP. ADAMTS13 activity was undetectable and ADAMTS13 inhibitor levels were elevated. Rituximab and caplacizumab were then added. Symptoms of encephalopathy improved by day five and platelet counts started improving by day nine. After several days of plasma exchange, he showed a "clinical response" with several weeks of active treatment. The association between coronavirus disease 2019 (COVID-19) infection and the severity of TTP with multiorgan failure is not well understood yet. Although we describe a successful multimodal approach to the management of TTP, which we believe is secondary to COVID-19 infection, further research is warranted to analyze and understand the pathophysiology by which COVID-19 infection causes TTP. It would help in establishing standardized therapy in the future.