Nonhormonal explanations for sex discrepancy in human illness

Autoimmune illnesses have sex ratios that range from 10:1 female predominant to 1:3 male predominant. Potential genetic/chromosomal explanations include differences in X and Y chromosome genes, mutations or deletions of sex chromosomes, skewed inactivation of X chromosome genes, and gene imprinting. The latter may reflect epigenetic environmentally induced differences between the sexes. In addition, environmental exposure differences may explain sex differences in disease incidence. Pregnancy adds its own set of differences that may change susceptibility to autoimmune illnesses. Biological sex differences in immune function, especially those induced by sex hormones, are less likely explanations of sex differences.