"An ulcer" is a symbol of an extremely grave moral, spiritual disease of a person, the consequences of a prolonged violation of the moral and spiritual Laws, the Commandments established by God.

"An "ulcer" is also a symbol of a difficult to "cure," especially a markedly pronounced, severe moral, spiritual vice of a person or society.       

"Plagues" is also a symbol of a particularly strong, pronounced, extremely painful, devastating test by peoples of the consequences of their rejections, violations of God's Commandments