A yiddish word often used in medicine to describe fakey diseases that exist only in a patient's mind, such as fibromyalgia, tension headaches, restless legs syndrome, irritable bowel syndrome, multiple chemical sensitivity, ambien sleep-eating syndrome, POTS, chronic fatigue syndrome, and any other form of what used to be called neurasthenia.
Louis R: "Oh Doctor Heather, I just cannot function anymore because of my chronic fatigue syndrome in addition to my totally disabling other neurasthenic complaints!"
Doctor Heather: "You know what Louis? I think you suffer from the very rare and deadly Mishugenosis. I am going to fill out your SSI and your Family Medical Leave Act papers right now, because you cannot work any more, not even a desk job! And here is a prescription for Adderall too, it cures everything!"