Background Systemic lupus erythematosus (SLE) is a female predominant autoimmune disorder. X chromosome contains the largest number of immune-related genes of entire human genome. The number of X chromosomes in an individual has been recognized as having a ‘dose effect’ in the proclivity of developing SLE. We investigate the proportion of individuals with Klinefelter syndrome (KS) karyoptype 47, XXY and karyotype 47, XXX with SLE compared with SLE in the general population.

Methods Multicenter retrospective cohort study utilizing a global federated research network database of electronic health records. Using ICD-10 codes, patients with KS karyotype 47, XXY and karyotype 47, XXX who developed SLE at any given time were identified and compared with proportion of SLE in general population from 1/1/2013 to 12/31/2022.

Results A total of 125,757,374 patients were queried on 1/16/2023 on the Global Collaborative Network. A total of 1,774 patients have KS; 2,582 patients have XXX; and 259,841 patients have SLE (224,230 or 86% female; 35,611 or 14% male with F:M ratio was 6:1 for all comers). A total of 21 patients with KS were found to have SLE; 19 patients with XXX have SLE. KS has a 41-fold increase in having SLE when compared with male SLE patients in the general population; and a 6.8-fold increase in SLE when compared with female SLE patients in general population. Karyotype 47, XXX patients have a 4.2-fold increase in SLE when compared with female SLE patients in general population.

Conclusions This real world, real-time cohort study showed a 6.8-fold increase in SLE in Klinefelter syndrome karyotype 47, XXY and a 4.2-fold increase in SLE in karyotype 47, XXX when compared with female SLE patients in the general population. Extra X chromosome in KS and XXX appear to have a non-proportional, synergistic effect on the risk of developing SLE.