Female predominance and X chromosome defects in autoimmune diseases.

It is known that autoimmune diseases cumulatively affect 5-10% of the general population. Although knowledge of pathogenesis has become more refined, laboratory diagnosis more accurate, and therapy more effective, the reasons for the female preponderance of these conditions remain unclear. The most intriguing theory to explain the female preponderance is currently related to sex chromosomes, as women with autoimmune diseases manifest a higher rate of circulating cells with a single X chromosome (i.e. X monosomy). In addition, there have been several reports on the role of X chromosome gene dosage through inactivation or duplication in autoimmunity. Taken together, sex chromosome changes might constitute the common trait of the susceptibility to autoimmune diseases.