Associations between Klinefelter's syndrome and autoimmune diseases: English national record linkage studies.

There are reports suggesting that people with Klinefelter's syndrome (KS) may be at increased risk of some autoimmune diseases, but the evidence is not substantial. We wanted to add to the evidence by systematically assessing the risk of autoimmune diseases in a national cohort of people with KS. We selected records of all people with KS in a record-linked dataset of all hospital day cases and inpatient admissions in England, 1999-2011; and we followed them up by electronic record linkage to identify the occurrence of autoimmune diseases.