Key Facts

  • Nontuberculous mycobacteria (NTM) are organisms commonly found in soil and water in many parts of the world.
  • The great majority of NTM lung disease in the U.S. is caused by Mycobacterium avium complex (MAC).
  • Everyone comes into contact with NTM, but it usually only causes infection in people with underlying lung disease, such as bronchiectasis or COPD, a weakened immune system or older age.
  • NTM disease is not contagious.
  • More than 86,000 people are likely living with NTM lung disease in the U.S. Rates appear to be increasing, especially among women and older age groups.
  • Some common symptoms of NTM lung disease are chronic cough, fatigue, weight loss, fever and night sweats.
  • Treatment of NTM typically requires taking multiple antibiotics, often for several years.

What Causes NTM Lung Disease?

Nontuberculous mycobacteria are a group of bacteria naturally found in soil, water and dust worldwide. Everyone inhales NTM into their lungs as part of daily life, and in most people the organisms do no harm. But in a small number of vulnerable individuals, NTM gets established in the lungs as an infection.

There are many species of mycobacteria known to cause disease in humans. The two most widely known are Mycobacterium tuberculosis, which causes tuberculosis, and Mycobacterium leprae, which causes leprosy. The other Mycobacterium species are classified as “nontuberculous” to clearly set them apart. Unlike the others, NTM lung disease is not known to be contagious.

The most common type of NTM bacteria in the U.S. is Mycobacterium avium complex (MAC). The great majority of NTM lung disease in the U.S. is caused by MAC. Two of the other more common NTM species that infect the lungs are M. abscessus and M. kansasii.

Each type of NTM affects the body differently. The severity of disease, how it is treated, and the likelihood of recovery can vary widely from person to person. Some of the factors that impact the course of someone’s NTM lung disease are the virulence of the organism, the amount of exposure they’ve gotten, and their overall health.

How NTM Lung Disease Affects Your Body

Most people who are exposed to NTM never get sick from it. The organism gets cleared from the lungs by the body’s natural defense system before it can cause infection. But in some people, especially those with a weakened immune system or an underlying lung disease such as COPD or bronchiectasis, the NTM organism is able to invade the lungs and cause an infection. The infection can cause inflammation and lung damage that worsens over time.

There are two forms of NTM lung disease. The less progressive form is sometimes called nodular bronchiectasis. The NTM infection causes inflammation of the airways, which over time causes them to become damaged and scarred. As the disease progresses, the damaged airways lose their ability to clear mucus normally, which invites recurring respiratory infections like bronchitis and pneumonia. Nodular bronchiectatic NTM disease is found most often in older women who have no smoking history.

The other more progressive form of NTM lung disease is called cavitary disease. The NTM infection in the lungs causes scarring, fibrosis and the formation of cavities or pits in the lung tissue. This damage can lead to respiratory failure. This form is most commonly found in people with a smoking history who also have existing lung disease such as COPD or bronchiectasis.

Some NTM organisms can cause disease in other parts of the body, including the lymph nodes, skin, soft tissue and bones.

Who Is at Risk for NTM Lung Disease?

Although anyone can get NTM lung disease, some groups of people are at much higher risk than the general public. These groups include:

  • People who have damaged lungs from diseases such as bronchiectasis, COPD, cystic fibrosis, silicosis or a previous tuberculosis infection
  • People with a weakened immune system, either due to having an autoimmune disorder such as rheumatoid arthritis or Sjogren’s disease, active HIV infection, or because they are taking immune suppressing medications such as prednisone or chemotherapy
  • Postmenopausal women
  • People over 65 years old

Some environments and behaviors are particularly conducive to NTM exposure, which can cause increased risk for vulnerable individuals. Because the bacteria are found naturally in the soil, any activity that stirs up dirt and dust increases the likelihood of breathing in the organisms. NTM also thrives in water and is commonly found in municipal water supplies and household plumbing. It is resistant to disinfectants such as chlorine and can survive at temperatures normally used in home hot water heaters. Showers, hot tubs and other steamy places are potential sources of NTM exposure.

Development of this educational content was supported by a collaborative sponsorship from Insmed Incorporated.

Page last updated: June 7, 2024

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