Development of mixed connective tissue disease and Sjögren's syndrome in a patient with trisomy X

Increased risk of developing systemic lupus erythematosus (SLE) has been reported in patients with Klinefelter syndrome. Here, we describe a 16-year-old Japanese patient with trisomy X (47,XXX) who developed mixed connective tissue disease (MCTD) and Sjögren's syndrome. She had polyarthritis, edematous fingers with Raynaud's phenomenon, sicca syndrome, interstitial lung disease, possible myositis, and was positive for anti-nuclear antibody, anti-nRNP antibody and rheumatoid factor. This is the first report in the literature of a case of MCTD with female polysomy X, which further supports the link between the presence of extra X chromosome(s) and the development of autoimmune diseases.