LAM lung disease (lymphangioleiomyomatosis) is a rare lung disease that tends to affect women of childbearing age.
In LAM lung disease, muscle cells that line the lungs' airways and blood vessels begin to multiply abnormally. These muscle cells spread into areas of the lung where they don't belong.
The air sacs in the lung also swell and form small pockets called cysts. As the cysts develop throughout the lungs, LAM causes breathing problems similar to emphysema.
The muscle cells can spread outside the lung, forming noncancerous tumors on organs in the abdomen and pelvis.
What Causes LAM Lung Disease?
No one knows what causes pulmonary lymphangioleiomyomatosis. Estrogen seems to be involved, because women rarely develop LAM before puberty or after menopause. Fewer than 10 men are known to have ever developed LAM lung disease.
Smoking isn't known to cause LAM: more than half of people with LAM lung disease have never smoked.
LAM is so rare that it's unknown how often it really occurs. For example, during a three-year study by researchers, fewer than 250 people with LAM were identified in the U.S. Fewer than 2,000 women are known to have LAM today.
LAM is not cancer, but appears similar to other conditions in which benign tumors grow uncontrollably. LAM lung disease shares some features with a different condition called tuberous sclerosis.
Symptoms of LAM Lung Disease
Most people with LAM lung disease experience shortness of breath. Other symptoms include wheezing and cough, which may be bloody.
Often, people with LAM develop a sudden pneumothorax (collapsed lung). This occurs when one of the cysts near the lung's edge ruptures, allowing inhaled air to compress the lung. A pneumothorax usually causes pain and shortness of breath.
If muscle cells migrate to areas outside the lungs, LAM can cause other symptoms:
- Chylous ascites: The flow of lymph is blocked by errant muscle cells. Chyle (milky lymph fluid) builds up in the belly.
- Angiomyolipomas: Noncancerous tumors may grow in the liver or kidneys. These can cause pain, bleeding, or kidney failure.
In a few people with LAM, discovery of these benign tumors outside the lungs is the first sign of LAM lung disease.
Diagnosis of LAM Lung Disease
Most people with LAM see their doctor because of shortness of breath. Because LAM is so rare, it's often misdiagnosed at first as asthma or emphysema.
Generally, LAM is finally discovered after a long workup for shortness of breath. Tests frequently performed include:
- Chest X-ray: In LAM, a chest X-ray may show fine lines in the lungs, where muscle cells have multiplied. In early stages of LAM lung disease, the chest X-ray film may look normal.
- Pulmonary function testsmeasure lung capacity and the ability to get oxygen from the air into the blood. These tests are usually abnormal in people with LAM.
- Computed tomography (CT scan): Chest CT scans are almost always abnormal in LAM lung disease. Cysts are usually visible. High-resolution CT (HRCT) may show the changes of LAM even more clearly.
It's possible to diagnose LAM lung disease based on a woman's history and findings on high-resolution CT scan. But doctors often recommend collecting a sample of lung tissue (biopsy) to confirm the diagnosis. Lung biopsies can be collected in different ways:
- Bronchoscopy: An endoscope (flexible tube with a camera on its end) is passed into the windpipe and lower airways. Tools passed through the endoscope can collect a lung biopsy.
- Thoracoscopy: An endoscope is passed through a small incision into the chest to collect lung tissue.
- Open lung biopsy: Traditional surgery in which a surgeon works through a larger incision in the chest and takes a sample of lung tissue.
A physician (pathologist) then examines lung biopsy tissue, helping make the diagnosis of LAM lung disease with greater certainty.
Treatment of LAM Lung Disease
The drug sirolimus (Rapamune) is the first drug approved to treat lymphangioleiomyomatosis. The drug has been found to help improve the lung capacity in patients, allowing them to breathe easier.
In addition, inhaled bronchodilators (albuterol, ipratropium) can help open the airways, reducing shortness of breath in some people. Patients with LAM lung disease should avoid smoking cigarettes as well as second hand smoke.
Because hormones like estrogen seem to be involved in LAM lung disease, treatments that manipulate hormone levels could help some people with LAM. A number of hormone-related treatments have been tested in women with LAM lung disease:
- Tamoxifen (Nolvadex, Soltamox)
- Synthetic luteinizing hormone-releasing hormones (Leuprolide, Lupron)
In clinical trials that tested these therapies, some women were helped, but others were not.
People who experience pneumothorax generally must undergo procedures to reinflate the collapsed lung, and prevent its recurrence.
If pulmonary lymphangioleiomyomatosis progresses and becomes disabling, lung transplantation may be an option. Though it's a drastic treatment, most people undergoing lung transplant for LAM lung disease gain improved lung function and quality of life after surgery.
What to Expect With LAM Lung Disease
Pulmonary lymphangioleiomyomatosis is progressive, and so far there is no cure. Most women with LAM experience a steady decline in lung function, with increased shortness of breath over time.
However, women vary widely in their experience of living with LAM lung disease. Some rapidly progress while others progress slowly: in some studies, nearly 90% of women were alive 10 years after diagnosis with LAM. However, surviving as long as 20 years after diagnosis is rare.
Researchers are working to identify how muscle cells go awry in LAM. Clinical trials of experimental drugs to treat LAM lung disease are also under way.