A Breakthrough in the Mystery of Why Women Get So Many Autoimmune Diseases
(The Atlantic) – About 65 million years ago, shortly after the time of the dinosaurs, a new critter popped up on the evolutionary scene. This “scampering animal,” as researchers described it, was likely small, ate bugs, and had a furry tail. It looked, according to artistic renderings, like an especially aggressive New York City rat. And it had a placenta, an organ that grows deep into the maternal body in order to nourish the fetus during pregnancy.
The rodentlike thing would become the common ancestor of the world’s placental mammals, with descendants that include whales, bats, dogs, and humans, among many other species. And today, the placenta might hold the key to one of the most enduring mysteries in human medicine: Why do women suffer much higher rates of autoimmune disease than men do?
Autoimmune diseases turn people’s own immune systems against their bodies. In the United States alone, women represent 80 percent of all cases of autoimmune disease. Women are 16 times more likely than men to get Sjogren’s syndrome, in which the immune system goes after the glands that make tears and saliva, and nine times more likely to have Hashimoto’s thyroiditis, in which it sets its sights on the thyroid. Sjogren’s forced Venus Williams to drop out of the U.S. Open in 2011. The singer Selena Gomez underwent a kidney transplant after suffering complications from lupus, which is eight times more common in women than in men.
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