Thrombocytosis in rheumatoid arthritis.

Of 75 patients with rheumatoid arthritis, 39 had a thrombocytosis and 36 normal platelet count. A highly significant relationship existed between the platelet count and disease severity and an inverse correlation with level of haemoglobin. An association appeared to exist between thrombocytosis and extra-articular manifestations of rheumatoid disease. By 75Selenomethionine labelling platelet and fibrinogen survival and turnover were determined. In 3 rheumatoid patients with thrombocytosis platelet survival was decreased and turnover increased. In these and a further rheumatoid patient with a normal platelet count there was reduced fibrinogen survival and increased fibrinogen turnover, and in addition excess fibrin degradation products were detected. The results suggest that thrombocytosis accompanies the more severe cases of rheumatoid disease and is due to a compensatory increase in platelet production associated with active intravascular coagulation.