CXCL4 is emerging as a key player in the pathogenesis of SSc, where it has been implicated in fibrosis, and in RA, where CXCL4 is highly expressed in inflamed synovium and has been proposed as one of most informative molecules for differential diagnosis and prediction of disease progression6,34,37,39. The gene discussed is PF4; the disease is rheumatoid arthritis.