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

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.

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.

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.

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.

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.