Why do autoimmune diseases disproportionately affect women?

Science · Published 11 October 2026 Swipe more like this →

In short: In the United States, between 24 and 50 million people live with autoimmune conditions. Remarkably, as many as 4 out of 5 of these individuals are women. Scientists are now tracing this massive disparity to a fundamental biological feature: the presence of two X chromosomes in every female cell.

In biological females, every cell contains two X chromosomes, whereas males possess one X and a much shorter Y chromosome. To prevent a lethal overproduction of proteins, the body uses a mechanism called X-chromosome inactivation. During early embryogenesis, each cell independently shuts down one of its two X chromosomes using a functional RNA called Xist. This process ensures that female cells produce the same amount of X-chromosome-specified proteins as male cells. Without this clever biological workaround, the massive overproduction of these proteins would be lethal.

A study published on February 1, 2024, in the journal Cell, led by Stanford Medicine's Howard Chang, PhD, has uncovered a potential link between this mechanism and autoimmunity. Researchers found that some proteins associated with the Xist RNP complex—the group of more than 80 proteins that work with Xist RNA—can be recognized by autoantibodies, the very proteins responsible for attacking the body's own tissues. This discovery offers a possible way to predict these conditions before they even manifest. Such breakthroughs could eventually lead to improved diagnostic testing and more effective treatments.

To test this, researchers used two strains of mice: one resistant to autoimmune diseases and one highly vulnerable. When scientists engineered males in the vulnerable strain to produce Xist, more than 60% of those males developed severe autoimmune disease following an environmental trigger. This suggests that the activity of Xist and its associated proteins may be a key driver in why women are at a much higher risk for disorders like lupus, rheumatoid arthritis, and Sjogren's syndrome. In the resistant strain, these engineered males did not develop the disease after exposure to a trigger. This highlights how the interaction between genetic factors and environmental stressors shapes autoimmune risk.

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