Thrombocytosis and thrombocytopenia in rheumatic diseases.

SIR, In their interesting abstract on platelets and rheumatoid arthritis' Farr et al. call attention to the frequent presence of an inflammation-related thrombocytosis in rheumatoid arthritis (RA). They point out that such a finding is not specific of RA. In fact they found thrombocytosis related to disease activity also in patients affected with Crohn's disease. We reached the same conclusions by the analysis of platelet counts found in a wide series including patients with RA, juvenile chronic arthritis (JCA), Sjogren's syndrome (SS), progressive systemic sclerosis (PSS), polymyalgia rheumatica with or without Horton's arteritis (PMR-HA), ankylosing spondylitis (AS), psoriatic arthritis (PA), and gout.23 We suggested that in the above mentioned diseases thrombocytosis should be considered as a nonspecific inflammation index, even if less useful than those commonly investigated. The clinician must therefore not be surprised to find thrombocytosis in a patient suffering from one of the above mentioned diseases. On the contrary, thrombocytopenia must lead to a careful evaluation. Actually we never found thrombocytopenia in patients with JCA (n=49), PMR-HA (n=14), AS (n=32), PA (n=36), SS (n=10), or gout (n=20). As regards RA we found only in 5 out of 162 patients a relatively low platelet count (between 120 and 150 x 109/l). Finally we found a relatively low platelet count (between 120 and 150 x 109/l) in onfy 3 out of 83 patients with PSS, in one of whom this finding coincided with the appearance of malignant hypertension. Therefore a finding of significant thrombocytopenia (platelet count less than 100 x 109/l) in a patient suffering from a rheumatic disease must make us suspect either adverse effects of drugs or a rheumatic disease different from the above-mentioned ones such as systemic lupus erythematosus and Felty's syndrome, or, as regards PSS, some particular conditions, such as intravascular coagulation occurring in scleroderma malignant hypertension or a recently described autoimmune thrombocytopenia.'