[Platelet function in systemic lupus erythematosus (author's transl)]. / Estudio de la función plaquetaria en el lupus eritematoso sistémico (LES).

The platelet function was studied in 23 patients with systemic lupus erythematosus, all of whom met the diagnostic creteria established by the American Rheumatism Association. They were not under any treatment, especially with any drug that might interfere with platelet function. The same study was performed on a control group composed of volunteers donors at a blood bank. The platelet count was definitely lower in the patients with lupus than in the control subjects (p less than 0.0005), although a clear thrombopenia was observed in only two indivduals (8.7 percent). Anti-platelet antibodies were found in only six cases (26 percent). There was a linear correlation between thrombopenia and the presence of hemorrhagic diathesis and low levels of C4 and CH50 components. Plateler adhesiveness was clearly lower in the lupus group than in the control group (p less than 0.0005). The presence of kidney disease determined a greater impairment of the platelet adhesiveness (p less than 0.0025). A notable defect on platelet aggregation was induced by ADP, adrenaline and collagen. This was more apparent in the group of patients exhibiting a higher degree of clinical activity and in those who showed a serum complement decrease. The mechanism responsible for this thrombopathy appears to be an interference in the platelet function due to the presence of circulating immunocomplexes. They adhere to the platelet membrane blocking its function and inhibiting the release of the necessary thrombocytic components for the second phase of the aggregation. This platelet alteration is not usually manifested clinically; for this reason no relationship was found between this platelet defect and the presence of hemorrhagic symptoms in our patients. The condition is reversible and may disappear after therapy with steroids and/or immunosuppresive agents.