Severe thrombocytopenia in antiphospholipid syndrome: a retrospective study of 432 patients

INTRODUCTION: Antiphospholipid syndrome (APS) is an autoimmune disease characterised by obstetric morbidity and recurrent venous and/or arterial thrombosis. It is frequently associated with systemic lupus erythematosus, and thrombocytopenia is a common manifestation. This study aimed to compare patients with APS, with and without thrombocytopenia, and to describe management and outcomes of severe thrombocytopenia. METHODS: We performed a retrospective single-centre study that included 432 patients with APS. Patients were divided into three groups according to the platelet count nadir: severe thrombocytopenia (< 50 G/L), moderate thrombocytopenia (between 50 and 130 G/L) and no thrombocytopenia (≥ 130 G/L). RESULTS: 142 patients developed thrombocytopenia during follow-up (32.9%): 57 (13%) had severe thrombocytopenia (< 50 G/L) and 85 (19.4%) had moderate thrombocytopenia (50-130 G/L). Patients with thrombocytopenia more frequently experienced thrombotic manifestations, including lower limb deep vein thrombosis (49% vs 37%, p=0.014), coronary thrombosis (15% vs 6.6%, p=0.006) and catastrophic antiphospholipid syndrome (CAPS) (27% vs 2.1%, p<0.001). Thrombocytopenia was more frequently associated with pre-eclampsia (16.8% vs 3.7%, p<0.001) and other APS manifestations, including skin (ulcer 4.9% vs 1.4%, p=0.046, cutaneous necrosis 7% vs 0.7%, p<0.001), cardiovascular (MINOCA 7% vs 0.7%, p<0.001, valvular disease 19.7% vs 9.3%, p=0.002), renal (18.3% vs 3.1%, p<0.001) and pulmonary (5.6% vs 1%, p=0.007) manifestations. Aetiologies of severe thrombocytopenia were mainly immune thrombocytopenia (ITP) and CAPS. In patients with severe thrombocytopenia, treatment followed the approach used for primary ITP, and anticoagulation was generally maintained even in the presence of bleeding episodes. Overall survival was poorer in patients with severe thrombocytopenia (p<0.0001). CONCLUSION: Our results suggest that thrombocytopenia is associated with a more severe APS phenotype and increased mortality.