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LAM Lung Disease (Lymphangioleiomyomatosis)

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.

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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 tests measure 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.

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