Objective Our aim was to present our first experience with the use of caplacizumab, an anti-von Willebrand factor monoclonal antibody, in an SLE patient who developed TTP. Data on the use of caplacizumab in SLE-associated TTP are scarce.

Methods We present a single SLE patient with TTP, successfully treated with plasma exchange, caplacizumab, and rituximab.

Results A 64-year-old patient was admitted to our department in 2023 due to severe thrombocytopenia (15x10⁹/L), multiple hematomas of the extremities, and a history of transient dysarthria lasting 30 minutes the evening prior to admission. Her previous history was remarkable for inactive SLE and splenectomy due to B-non-Hodgkin’s splenic lymphoma of the marginal zone in 2016. Her blood count was compatible with hemolytic anemia (hemoglobin 95 g/L, LDH 984 U/L, bilirubin 17 umol/L, haptoglobin undetectably low). Her anti-dsDNA levels were not increased, antiphospholipid antibodies and complement levels were normal, despite an elevated erythrocyte sedimentation rate (120 mm/h). Her brain CT and CT angiography were unremarkable. Given the negative Coombs test, an urgent peripheral blood smear was ordered, revealing the presence of 12 shistocytes per high power field, compatible with microangiopathic hemolytic anemia. Given that the patient was stable, she was started on pulse-dose iv methylprednisolone the same evening, and a blood ADAMTS13 test was ordered early in the next morning (0,05 kIU/L, reference range: 0.60–1.21). The patient was diagnosed with TTP and was treated with plasma exchange for three consecutive days, as well as caplacizumab 10 mg sc daily for the duration of plasma exchange and 30 days subsequently. She was also treated with rituximab iv 375mg/m2 body surface area (four consecutive weekly doses). Neither the chest-abdomen CT scan nor the bone marrow biopsy revealed signs of lymphoma relapse. Thrombocytopenia was resolved within a week following treatment initiation, and no relapse of TTP or SLE was observed within four months of follow-up.

Conclusions Even a history of transient neurological symptoms should warrant a diagnosis of TTP in the context of SLE with Coombs-negative hemolytic anemia. The role of caplacizumab in the therapeutic algorithm of TTP in SLE patients still needs to be established.