Women born from 1900 on were the first ones to experience night sweats, hot flashes, fatigue, panic attacks, anxiety, hair thinning, and joint pain when they reached a certain age. In the middle of the 20th century, a tidal wave of women ages 40 to 55 were visiting their doctors with these symptoms—and doctors didn’t know what to think. Behold, mystery illness and the autoimmune confusion were born. Medical professionals had never been so bewildered.