Background/Purpose: Antiphospholipid-associated syndrome refers to organ dysfunctions developed in the existence of antiphospholipid antibodies (aPL), apart from the typical manifestations of antiphospholipid syndrome (APS) such as thromboembolism and pregnancy morbidities. Thrombocytopenia is one of the aPL-associated manifestations and is reported in 20-40% of APS patients. Patients with thrombocytopenia and aPL are at risk of both bleeding and thrombosis. The evaluation of the coagulation status in patients with thrombocytopenia is particularly difficult and the clinical profile of APS patients with thrombocytopenia has not been fully elucidated. The purpose of this study is to analyze the clinical profile of patients with primary APS and thrombocytopenia and to examine the relation between the risk of thrombosis and thrombocytopenia.

Methods:  This study comprised of 57 consecutive patients with primary APS and 72 autoimmune disease control patients (non-systemic lupus erythematosus) who visited Hokkaido University Hospital Rheumatology Clinic between January 2000 and May 2014. Thrombocytopenia was defined as a platelet count less than 100,000 per microliter, persistent on two occasions more than 12 weeks apart and without no underlying causes besides aPL. Primary APS patients were retrospectively followed-up for the incidence of thrombosis. Kaplan-Meier survival probability estimate was performed to analyze the occurrence of thrombotic events in primary APS patients with and without thrombocytopenia.

Results: The median age of patients was 41 years (IQR 32-50) in primary APS patients and 50 years (IQR 31-59) in the control group. Thrombocytopenia was more frequently diagnosed in patients with primary APS 17/57(30%) than in the control group 4/72(6%), p<0.001.   

In primary APS group, arterial thrombosis was developed in 9 patients (16%) throughout the follow-up period (106 months [IQR 36-142]) ; 8 patients had cerebral infarctions and 1 myocardial infarction. Arterial thrombosis was more frequently developed in patients with thrombocytopenia than in those without (6/17(35%) vs. 3/40(8%), p=0.014), while no correlation was found between venous thrombosis and thrombocytopenia. There was no statistically significant difference in the rate of hemorrhagic event between APS patients with and without thrombocytopenia (1/17 (6%) vs. 0/40 (0%), p=0.298). Kaplan-Meier curve revealed that the inferior survival was associated with thrombocytopenia (6/9(67%) vs 11/48(23%), p=0.047 log-rank test: Figure1).

Conclusion: Thrombocytopenia in APS patients represents a risk factor for arterial thrombosis and not for bleeding. The risk of thrombosis associated with thrombocytopenia in primary APS must be carefully evaluated and, if necessary, appropriate antithrombotic therapy administered. 

---

« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/thrombocytopenia-in-primary-antiphospholipid-syndrome-is-related-to-arterial-thrombosis/