How Is LAM Diagnosed?

Methods for diagnosing LAM have improved, and it is now possible to diagnose it at an early stage.

Many of the signs and symptoms of LAM can be caused by other diseases such as asthma, emphysema, and bronchitis. It is important for your doctor to rule out those conditions before making a final diagnosis.

• Chest x ray. A chest x ray takes a picture of your heart and lungs. It can show a collapsed lung or fluid in your chest cavity. In the early stages of LAM, your chest x rays may look normal, but as the disease gets worse, they may show cysts in your lungs.
• Lung function tests. For these tests, you breathe through a mouthpiece into a machine called a spirometer (spi-ROM-e-ter). The spirometer measures the amount of air you inhale and exhale and how fast your lungs move it in and out. These tests also can provide an estimate of the amount of air your lungs can hold, and how well your lungs can take oxygen into the bloodstream.
• Exercise stress test. This test helps the doctor evaluate the effect of exercise on your heart and lungs.
• Blood tests. The doctor takes a sample of your blood from an artery in your arm and examines it to see whether your lungs are providing enough oxygen to your blood. These tests may show low oxygen levels in your blood even when you are resting. The doctor also may take a blood sample from a vein in your arm to look at your blood cells and blood chemistry.
• Pulse oximetry. A small sensor attached to your fingertip also can give an estimate of the level of oxygen in your blood.
• High-resolution CT scan (HRCT). This test shows a computer-generated picture of your lungs that has more detail than a chest x ray. It is the most useful imaging test for diagnosing LAM. HRCT can show cysts or shadows of cell clusters in your lungs, a collapsed lung, or enlarged lymph nodes. It also can show how much normal lung tissue has been replaced by the LAM cysts. HRCT scans of your abdomen and pelvis can show if you have growths in your kidneys, other abdominal organs, or lymph nodes.
• Lung biopsy. Although the tests mentioned above sometimes provide enough information for your doctor to diagnose LAM, the most useful test involves removing samples of your lung tissue so they can be looked at under a microscope. You should go to a doctor who specializes in LAM for this test. Several procedures can be used to obtain lung tissue:
  • Thoracoscopy (tho-rah-KOS-ko-pe). Your doctor inserts a small, lighted tube (endoscope) into little incisions in your chest wall. This lets him or her see the insides of your chest and snip out a few small pieces of lung tissue. This procedure is done in a hospital, and you are under general anesthesia. It is not major surgery, but it usually provides all the tissue your doctor needs.
  • Open lung biopsy. Your doctor removes a few small pieces of lung tissue through an incision in your chest wall between your ribs. This procedure also is done in the hospital, and you are under general anesthesia. Recovery takes longer than recovery from thoracoscopy.
  • Transbronchial biopsy. Your doctor inserts a long, narrow, flexible, lighted tube (bronchoscope) down your windpipe, or trachea (TRA-ke-ah), into your lungs. He or she then snips out bits of lung tissue with a tiny forceps. This procedure is usually done in a hospital on an outpatient basis, and you are under local anesthesia. Doctors usually are not able to remove enough tissue to diagnose LAM with this procedure.

Some doctors recommend that once you are diagnosed with LAM, you have magnetic resonance imaging (MRI) of your head. This test can show if you have signs of tuberous sclerosis complex (TSC) or a growth in your brain called a meningioma (me-NIN-je-O-mah). About 1 out of every 20 patients with LAM has this kind of growth. It also appears in people with TSC.

The National Institutes of Health is studying whether blood tests for the TSC1 and TSC2 genes may be helpful in diagnosing LAM patients.