Antiphospholipid syndrome (APS) is characterized by the occurrence of venous or arterial thrombosis and/or an adverse pregnancy outcome due to the presence of antiphospholipid antibodies (aPL) 1. There are to types of APS: either primary or secondary in the presence of an underlying disease, usually systemic lupus erythematosus (SLE).
Thrombocytopenia (low platelets) is frequently observed in APS patients, with an incidence ranging from 22 to 42 percent 2. The frequency of thrombocytopenia is higher in SLE-associated APS than in primary APS. According to uptodate 3:
the degree of thrombocytopenia is usually moderate, with a platelet
count usually in the range of 100,000 to 140,000/microL, and is rarely
associated with hemorrhagic events. Thrombocytopenia does not preclude
the occurrence of thrombotic complications of APS.
Now to your question, here are the recommendations in uptodate (which is a common source of reference for clinicians, as it provides, uptodate information of guidelines and recommendations):
For patients with thrombocytopenia who develop a thromboembolic event
an antithrombotic therapy with low molecular weight heparin and
vitamin K antagonists (goal INR 2.0 to 3.0) should be initiated as in
other patients with APS.