Autoimmune Thrombocytopenia

Thrombocytopenia is found in 25-40% of patients with APS, and is one of the most common presenting manifestations. Among these patients, thrombocytopenia is more frequently observed in patients with SLE than in patients with PAPS.

aPL-related thrombocytopenia is a chronic, usually mild and is seldom associated with hemorrhagic complications. Bleeding may be related to several causes other than thrombocytopenia:

Table 7.7. Hematologic disorders in APS.

Autoimmune thrombocytopenia Autoimmune hemolytic anemia Microangiopathic hemolytic anemia Thrombotic thrombocytopenic purpura (TTP)

high-intensity anticoagulation, hypoprothrombinemia (associ-tated with LA), and acquired defects of platelet function often associated with aPL. Values lower than 50 x 109 platelets/L are uncommon, although platelet count can fluctuate with time. Severe thrombocytopenia is an additional risk factor for bleeding complications in these patients. Arterial and/or venous thrombosis in APS may occur despite very low platelet count; however, the frequency of aPL-associated throm-botic events may be lower when platelet count is less than 50 x 109 L.

The pathogenic role for aPL in thrombocytopenia is still controversial. aPL may have a role in thrombocytopenia, but there may be other factors, such as antibodies to platelet membrane glycoproteins, found in 60% of these patients.

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