Pharyngitis /færɨnˈdʒaɪtɨs/ is the inflammation of the pharynx, a region in the back of the throat. In most cases it is quite painful, and it is the most common cause of a sore throat.Like many types of inflammation, pharyngitis can be chronic or acute (quickly developing and temporary). Pharyngitis can result in very large tonsils, which cause trouble swallowing and breathing.