In terms of number of X chromosomes, women with Turner's syndrome cytogenetically resemble men. An increased risk of autoimmune diseases has been observed among women with Turner's syndrome. This study was undertaken to investigate whether the autoimmune disease profile in women with Turner's syndrome is characterized by diseases with a female or male predominance.

Using the Danish Cytogenetic Central Register, the Danish National Patient Register, and the Danish Civil Registration System, we estimated relative risk of 46 different autoimmune diseases in a cohort of 798 Danish women with Turner's syndrome followed up for 12,461 person‐years between 1980 and 2004. Standardized incidence ratios (SIRs) of first hospitalization for autoimmune disease and 95% confidence intervals (95% CIs) were used as measures of relative risk.

The overall risk of autoimmune disease among women with Turner's syndrome was twice that among Danish women in general (SIR 2.1 [95% CI 1.6–2.7]). For autoimmune diseases with a female predominance, the SIR among women with Turner's syndrome was 1.7 (95% CI 1.2–2.4), whereas the SIR for autoimmune diseases with a male predominance among these women was 3.9 (95% CI 2.5–5.8). Associations were strongest for Hashimoto thyroiditis (SIR 14.6 [95% CI 6.7–27.1]), a strongly female‐predominant condition, and type 1 diabetes mellitus (SIR 4.1 [95% CI 2.5–6.3]).

Women with Turner's syndrome are at excess risk of autoimmune diseases, notably autoimmune diseases characterized by male predominance.