Abstract
The article summarizes data on the association of Klinefelter syndrome (KS) with autoimmune rheumatic diseases, that is rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), polymyositis/dermatomyositis, systemic sclerosis (SSc), mixed connective tissue diseases (MCTD), Sjogren’s syndrome and antiphospholipid syndrome (APS). Recently, a higher risk for RA, SLE and Sjogren’s syndrome in patients with KS has been clearly demonstrated. However, the association of other autoimmune rheumatic disorders such as dermatomyositis/polymyositis, SSc, MCTD and APS is reported only casually. Based on the hormonal changes in KS, there are suggestions that low androgen and higher estrogen levels might be a predisposing factor for the development of autoimmune diseases, but evidence for the association is poor. Epidemiologic studies on larger cohorts of patients are required.