Thrombocytopenia in high-risk patients with antiphospholipid syndrome

Background: Thrombocytopenia is the most common non-criteria hematological feature in patients with antiphospholipid syndrome (APS). This condition is more common in patients with catastrophic APS (CAPS). Objectives: To evaluate the prevalence of thrombocytopenia in a large series of high-risk patients with APS, and to assess the behavior of the platelet count during CAPS. Methods/Patients: This was a cross-sectional study in which we analyzed the platelet counts of a homogeneous group of high-risk APS patients (triple-positive). Six of these patients developed a catastrophic phase of the disease, and the platelet count was recorded before the acute phase, during the acute phase, and at recovery. Results: The mean platelet count in 119 high-risk triple-positive patients was 210 +/- x 10(9) L-1. With a cut-off value for thrombocytopenia of 100 x 10(9) L-1, the prevalence of thrombocytopenia was 6% (seven patients). No difference between primary APS and secondary APS was found. In patients who suffered from CAPS, a significant decrease from the basal count (212 +/- 51 x 10(9) L-1) to that at the time of diagnosis (60 +/- 33 x 10(9) L-1) was observed. The platelet count became normal again at the time of complete remission (220 +/- 57 x 10(9) L-1). A decrease in platelet count always preceded the full clinical picture. Conclusions: This study shows that, in high-risk APS patients, the prevalence of thrombocytopenia is low. A decrease in platelet count was observed in all of the patients who developed the catastrophic form of the disease. A decrease in platelet count in high-risk APS patients should be considered a warning signal for disease progression to CAPS.