What Is LAM

Lymphangioleiomyomatosis (LAM) is a progressive lung disease that usually strikes women during their childbearing years.  Lymphangioleiomyomatosis is pronounced lim-fan-gee-o-ly-o-my-o-ma-to-sis.  “Lymph” refers to the lymph vessels and “angio” refers to the blood vessels. “Leiomy” means smooth muscle, “oma” is a tumor, and “tosis,” refers to a disease condition.

LAM is a systemic neoplasm that results in cystic destruction of the lung.  It is characterized by an abnormal growth of smooth muscle cells.  These cells invade lung tissues, including the airways, and blood and lymph vessels.  Although these cells are not considered cancerous, they grow uncontrollably within the lungs.  Over time, the cells form bundles in the walls of the airways, as well as the blood and lymph vessels, causing them to become obstructed.  These cells produce materials that break down tissue causing the formation of cysts.  The delicate architecture of the lungs is destroyed and the airflow is blocked limiting the delivery of oxygen to the rest of the body.

LAM manifests itself in a wide variety of ways, so it is sometimes difficult to diagnose.  The difficulty of the diagnosis is compounded by the fact that a lot of the symptoms of LAM are similar to those of other lung diseases such as asthma, emphysema, and bronchitis.  Chest x-rays are not usually sufficient to detect LAM, but a high-resolution chest CT scan can detect the characteristic cystic structure of LAM, thus providing an accurate diagnosis, if other manifestations of the disease (e.g., benign kidney tumor, lung collapse, or fluid in the lungs) are present.  In some circumstances, a lung biopsy may be needed to provide an accurate diagnosis.

The cause of LAM remains unknown, and although great strides have been made in researching the disease, no cure is yet available.  A recently completed treatment trial (the MILES Trial) suggested that a drug called sirolimus, or rapamycin, may improve lung function in some women with LAM.

How LAM Affects the Lungs

When you breathe, oxygen passes through the tiny airspaces (alveoli) in the lungs and then through tiny blood vessels called capillaries.  Normally, alveoli have walls that are only two cells thick.  But as the smooth muscle cells of LAM multiply, these walls thicken, and oxygen can no longer pass through them efficiently.

As it becomes more difficult for the oxygen to pass into your bloodstream; your blood-oxygen level drops.  That drop, in turn, forces your heart to work harder to pump oxygen to the various parts of your body.  In order to deliver adequate oxygen, the body may try to compensate by producing more red blood cells.   The growth of the cells also makes the structure of the lung less elastic.  This loss of tissue flexibility causes the person with LAM to have difficulty moving air both into and out of the lungs.  This airflow obstruction makes you short of breath, a condition called dyspnea.

The thickening of the alveolar walls also results in a breakdown of the lung tissue and the formation of air-filled cavities, called blebs or cysts.  As the disease progresses, there can be more extensive growth of smooth muscle cells throughout the lung and an increasing number of cysts formed.

The Course of LAM

We know that LAM is a progressive disease, but its progression is usually very slow.  In some women, however, the disease progresses at a rapid rate.  Doctors are working to find indicators that will help determine who will have a more rapid rate of progression and who will progress more slowly.  Whether the disease progression is slow or rapid, lung function tends to decrease over time, and many LAM patients will, at some point, require oxygen therapy.  Lung transplantation is often considered as a last resort.  While many women with LAM add several years to their lives through lung transplantation, it is not a cure.

What You May Expect

LAM affects each woman quite differently.  Some women have no symptoms; others have more than one.  Previously, the initial prognosis for a LAM patient was poor, but we have since learned that this was due primarily to LAM being diagnosed only in the advanced stages of the disease.  Newer technologies such as the high-resolution CT (HRCT) scan have allowed for a much earlier diagnosis.  In many cases, a woman’s diagnosis has been accidental—for example, when a CT scan was done for a totally unrelated reason.  Now, investigators believe that some women who have LAM may never be diagnosed because their symptoms are too mild to be brought to medical attention.

LAM patients have been followed at the National Heart, Lung, and Blood Institute (NHLBI) at the National Institutes of Health (NIH) since 1995, and researchers have learned a great deal about how LAM affects each woman differently.  Many women with LAM live much longer than previously predicted.  Remember: the rate of progression and the incidence of resulting symptoms can—and does—vary considerably among patients.

While many questions about LAM have yet to be answered, the extraordinary progress in understanding the disease has provided real hope that a treatment and possibly a cure for LAM can be achieved.

The Epidemiology of LAM

LAM is a disease that occurs almost exclusively in women.  All races are affected, and women with LAM have been identified in over sixty countries.  The average age of women at the time of diagnosis is approximately forty-eight, though, at the time of diagnosis, the reported age range is quite large—from six to seventy-five years of age.  Also, most women with LAM have had symptoms for three to five years before ultimately being diagnosed.  

Although LAM is considered to be a rare disease, researchers believe that it is not as rare as previously thought.  Current estimates of the incidence of LAM are based on data from registries in the United States, France, and the United Kingdom, three countries where there have been substantial organized efforts in contacting pulmonary physicians to determine the number of patients with LAM.  As previously mentioned, because LAM is relatively uncommon, it is often misdiagnosed.   Therefore, the current number of women diagnosed with LAM does not accurately represent the true prevalence of the disease.  Rough estimates suggest that there could be as many as 30,000 to 50,000 women worldwide who actually have sporadic LAM.