Actinomycosis, ak tuh nuh my KOH sihs, is a rare, infectious disease that affects human beings. It is characterized by the formation of painful abscesses in the mouth, lungs, or digestive organs. These abscesses grow larger as the disease progresses, often over a period of months. In severe cases, the abscesses may bore through bone and muscle to the skin, where they break open and leak large amounts of pus. Actinomycosis can destroy a person's jaw or lungs. It can also block the passage of food through the digestive system. It occurs in cattle and other animals as a disease called lumpy jaw. This name refers to the large abscesses that grow on the head and neck of the infected animal.