This particular type of polyp is a small swelling along the vocal chords, common among people who use their voices often, such as singers and actors. Symptoms include hoarseness, a "rough" or "scratchy voice," neck pain and body fatigue.
Smoking can also cause or aggravate polyps, but while one might assume Jon is a heavy smoker like Don Draper, he actually quit more than 20 years ago; on set, he puffs on herbal cigarettes that don’t contain any tobacco or nicotine.
The 42-year-old isn't the only celebrity to suffer from this affliction. Adele was famously forced to cancel her U.S. tour in 2011 to recover from vocal polyp surgery, while country music star Keith Urban postponed several performances after having a polyp removed that same year.