The First Case Report of 47,XXY/46,XX/46,XY Mosaic Klinefelter Syndrome Patient With Mixed Connective Tissue Disorder

Klinefelter syndrome (KS) mosaicism 47,XXY/46,XX/46,XY is an extremely rare disorder. Mixed connective tissue disorder (MCTD) is a systemic rheumatological disease with overlapping characteristic features of systemic lupus erythematosus (SLE), systemic sclerosis (SSc), polymyositis (PM)/dermatomyositis (DM), and rheumatoid arthritis (RA). It contains a higher titer level of U1-RNP and anti-RNP antibodies. A 50-year-old man was referred to our clinic with gynecomastia, lower extremity rash, persistent fever, arthralgia, muscle weakness, dry eye and mouth, Raynaud's phenomenon abnormal, and hormone levels. He was a follow-up patient for MCTD. Chromosome analysis of the patient revealed an abnormal karyotype of mos47,XXY/46,XX/46,XY. Fluorescence in situ hybridization (FISH) analysis indicated ish(SRYx1),(DZYx1)(DZX1x2)/ish (SRYx0),(DYZ1x0)(DZX1x2)/ish(SRYx1), (DZYx1)(DZX1x1). Although the prevalence of autoimmune diseases in Klinefelter syndrome is unknown, it is thought that the estimated frequency is higher than men, close levels to that of women. This might be explained by several genes that regulate the function of the immune system located on the X chromosome and the gene dosage mechanism that is the escape of X-inactivation in early embryogenesis for KS development. To the best of our knowledge, this is the first case to report a 47,XXY/46,XX/46,XY Klinefelter syndrome patient with MCTD.