Actinomycosis is a long-term (chronic) bacterial infection that commonly affects the face and neck.

Actinomycosis is usually caused by an anaerobic bacteria called Actinomyces israelii, which is a common and normally not disease-causing (nonpathogenic) organism found in the nose and throat.

Because of the bacteria's normal location in the nose and throat, actinomycosis most commonly appears in the face and neck. The infection is not contagious.

Symptoms occur when the bacteria enters the facial tissues after trauma, surgery, or infection. A common cause is dental abscess or oral surgery. Once in the tissue, it forms an abscess, producing a hard, red-to-reddish-purple lump, often on the jaw, from which comes the condition's common name, "lumpy jaw."

Eventually, the abscess breaks through the skin surface to produce a draining sinus tract. Actinomycosis can sometimes occur in the chest (pulmonary actinomycosis) and abdomen or other areas of the body.

• Draining sores in the skin, especially on the chest wall from lung infection with Actinomyces
• Fever
• Minimal or no pain
• Swelling or a hard, red-to-reddish-purple lump on the face or upper neck
• Weight loss

See also: Neck lumps

• Culture of the tissue or fluid shows Actinomyces species.
• Examination of drained fluid under a microscope shows "sulfur granules" in the fluid. They are yellowish granules made of clumped organisms.
• Examination under a microscope shows the Actinomyces species of bacteria.