Delayed Thrombotic Complications in a Thrombotic Thrombocytopenic Purpura Patient Treated With Caplacizumab

Thrombotic thrombocytopenic purpura (TTP) is a rare and unpredictable disease with a high mortality rate (90%) if untreated. It results from systemic microvascular thrombosis and leads to profound thrombocytopenia, hemolytic anemia and organ failure of varying severity. However, macrovascular thrombosis has been described in very rare cases. Caplacizumab has emerged as a promising new drug for the management of TTP. We report the case of a patient with idiopathic refractory TTP treated with caplacizumab who developed thrombotic complications upon discontinuation of treatment.

[Management of thrombocytopenia]

Thrombocytopenia is defined by a platelet level below 150 G/l. However, the limit of 100 G/l seems more appropriate to determine which thrombocytopenia will require further investigation. Initially, a thorough medical history should be performed as well as screening for any signs of bleeding. After having excluded the presence of platelet aggregates, it should be determined whether thrombocytopenia is isolated or associated with other abnormalities (cytopenias, coagulation disorder, abnormal renal or liver tests). Causes of thrombocytopenia along with the biological tests to achieve diagnosis, will be detailed in this article. We will then determine the medical emergencies that will need to be addressed to a reference center : active bleeding, biological signs of disseminated intravascular coagulation, acute renal failure, platelet count < 30 G/l (or < 50 G/l if the patient is on anticoagulation or antiplatelet therapy), significant and/or brutal onset pancytopenia. Outside these situations where vital prognosis is engaged, the patient should be rapidly addressed in case of platelet count between 30 and 50 G/l without any concomitant anticoagulation or antiplatelet therapy. Platelet levels between 50 and 100 G/l will require investigation, without any urgency, in outpatient haematology clinic.