Definition of Atypical mycobacterial infection:

Atypical mycobacterial infection is an illness caused by a type of mycobacterium other than tuberculosis.

Causes, incidence, and risk factors:

Atypical mycobacteria can cause a wide variety of infections such as abscesses, septic arthritis, and osteomyelitis (bone infection). They can also infect the lungs, lymph nodes, gastrointestinal tract, skin, and soft tissues.

There are many different species of mycobacterium other than tuberculosis (Mycobacterium tuberculosis). Some of the most common are listed below:

• Mycobacterium avium-intracellulare frequently affects AIDS patients and causes lung disease.
• Mycobacterium marinum cause skin infections and is also responsible for swimming pool granuloma.
• Mycobacterium ulcerans cause skin infections.
• Mycobacterium kansasii causes lung disease.

The rate of atypical mycobacterial infections is rare, but it is increasing as the AIDS population grows. Populations at risk include individuals who have lung disease and weakened immune systems (immunosuppression).