Hematologic Abnormalities in the Antiphospholipid Syndrome

The antiphospholipid syndrome is characterized by arterial/venous thrombosis and recurrent pregnancy loss in the presence of antiphospholipid antibodies in laboratory tests. There are well-documented additional associations between antiphospholipid antibodies and several abnormalities of specific cellular components of the blood, such as thrombocytopenia, hemolytic anemia, and, less frequently, leukopenia. The main hematological manifestations seen in patients with antiphospholipid antibodies are thrombocytopenia, usually mild, and hemolytic anemia with positive Coombs test. In the present chapter we first discuss the relationship between antiphospholipid antibodies and platelets, the proposed mechanisms causing thrombocytopenia in the antiphospholipid syndrome, and the treatment of thrombocytopenia in patients with antiphospholipid antibodies. In the second place, we comment on the relationship between antiphospholipid antibodies and erythrocytes focusing on both the positive Coombs test hemolytic anemia and the microangiopathic hemolytic anemia as part of thrombotic microangiopathic syndromes. Finally, we review leukocyte abnormalities referred to be related to antiphospholipid antibodies, mainly leukopenia and lymphopenia.