The diagnosis of LAM can be difficult because many of the early symptoms are similar to those of other lung diseases, such as asthma, emphysema, or bronchitis. Often the person with LAM first goes to the physician complaining of chest pain and shortness of breath that was caused by a pneumothorax.
Some patients first consult their physician because of shortness of breath upon exertion or a collapsed lung.
There are a number of tests the physician can do to confirm or rule out the existence of LAM.
This is a simple procedure that provides a picture of the lungs and other tissue in the chest. The chest x-ray is used to diagnose a pneumothorax or the presence of fluid in the chest cavity (pleural effusion). Smooth muscle cysts, consistent with LAM, do not usually appear on an x-ray.
Pulmonary Function Tests
The patient breathes through a mouthpiece into a machine (spirometer) that measures the volume of air in the lungs, the movement of air into and out of the lungs, and the movement of oxygen from the lungs into the blood.
The patient's blood is analyzed to determine whether the lungs are providing an adequate supply of oxygen to the blood.
Computed Tomography (CT)
Computed tomography (CT) is the most definitive imaging test for diagnosing LAM.
The patient lies inside a long, cylindrical structure, and x-ray beams pass through the body from different angles, producing multiple images. A computer combines all of these images and provides a 3-dimensional picture of the inside of the lungs and chest. This is called a CT scan.
On a CT scan, the presence of thin-walled cysts spread relatively uniformly throughout the lungs usually means LAM.
A CT scan should also be done of the abdominal area, as there is a benign kidney tumor called angiomyolipoma that is associated with LAM.
Two or more of the manifestations listed above (cysts, fluid in the lungs, benign kidney tumor, and collapsed lung) can give a clear diagnostic of LAM. An open lung biopsy should be performed as a last resort to diagnose LAM. In this procedure, a few small pieces of lung tissue are removed through an incision made in the chest wall between the ribs.
Another procedure, thoracoscopy, is also being used in some patients to obtain lung tissue. In this procedure, tiny incisions are made in the chest wall, and a small lighted tube (endoscope) is inserted so that the interior of the lung can be viewed, and small pieces of tissue are removed.
Both procedures must be done in the hospital under general anesthesia. Another technique, called transbronchial biopsy, may also be used to obtain a small amount of lung tissue. A long, narrow, flexible, lighted tube (bronchoscope) is inserted down the windpipe (trachea), and into the lungs. Bits of lung tissue are sampled, using a tiny forceps. This procedure is usually done in a hospital on an outpatient basis under local anesthesia. It is less reliable than an open lung biopsy because the amount of tissue that can be sampled is sometimes inadequate for diagnostic studies.
After the lung tissue is removed, it is examined in a pathology laboratory for the presence of the abnormal muscle cells and cystic changes characteristic of LAM.
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