Thrombocytopenia as a thrombotic risk factor in patients with antiphospholipid antibodies without disease criteria.

Introduction: The antiphospholipid syndrome (APS) is an acquired immune disorder defined by the presence of thrombosis (arterial and/or venous) and/or pregnancy morbidity along with the presence of positive antiphospholipid antibodies (aPL). There is a clear relationship between aPL and some events not included in the clinical criteria, including haematologic.

Objectives: a) to study the probability of developing clinical APS in patients with positive aPL and thrombopenia; b) to identify potential risk factors for thrombosis, and c) to study the association between thrombocytopenia and aPL.

Methods: A retrospective study of 138 patients with positive aPL without fulfilling clinical criteria for APS. Thrombocytopenia was defined as a platelet count≤100,000/μl. Patients with other causes of thrombocytopenia were excluded.

Results: Seventeen of the 138 (12%) patients in the study had thrombocytopenia. The mean platelet count was 60,000/μl. The risk of developing thrombocytopenia was higher in smokers (OR 2.8; P=.044), in those with lupus anticoagulant (OR 13.5; P<.001) and those with higher burden of aPL (OR 50.8; P<.001). After a mean follow-up of 146±60.3 months, 5 patients with thrombocytopenia (29.4%) developed thrombosis.

Conclusions: In our series, the incidence of thrombocytopenia is 12%. aPL-positive patients who develop thrombocytopenia have a potential risk of developing thrombosis. Tobacco could be a risk factor for thrombocytopenia. Autoantibodies load is a risk factor for the development of thrombocytopenia.