Characteristics of the clinical findings in patients with idiopathic thrombocytopenic purpura who are positive for anti-phospholipid antibodies.

It has been reported that anti-phospholipid antibodies are detected in some patients with idiopathic thrombocytopenic purpura (ITP). To study the significance of determination of anti-phospholipid antibodies in patients with ITP, clinical and laboratory findings were compared between patients whose sera were positive for these antibodies (Group A) and non-positive patients (Group B). Anti-cardiolipin antibody (aCL) was determined by enzyme-linked immunosorbent assay and lupus anticoagulant (LA) was determined by activated partial thromboplastin time (aPTT) and thromboplastin time inhibition test. Seven out of 27 cases of ITP belonged to Group A and 3 of the 7 were confirmed to have anti-phospholipid antibody syndrome (APS). There was a tendency for habitual abortion, and thrombosis, megakaryocytes in the bone marrow and platelet-associated IgG (PAIgG)-positive cells were more frequent in Group A than in Group B. However, it was difficult to discriminate APS from ITP alone, when there were no symptoms or signs of APS. Therefore, measurement of anti-phospholipid antibodies in ITP was thought to be useful for the differential diagnosis of APS and subsequently for the prevention of thrombosis.