What is LAM?
Lymphangioleiomyomatosis (lim-FAN-je-o-LI-o-MI-o-ma-TO-sis) is a rare lung disease that usually strikes women during the prime of their lives. Known as LAM for short, this disease is characterized by an abnormal growth of smooth muscle cells, especially in the lungs, lymphatic system and kidneys. Unregulated growth of these cells can lead to loss of lung function, accumulation of lymph rich-fluid in the chest and abdomen and growth of tumors in the kidneys. There are two forms of LAM, Sporadic LAM (S-LAM) and Tuberous Sclerosis LAM (TSC-LAM). S-LAM occurs for unknown reasons. LAM also can occur in women who have a rare disease called tuberous sclerosis complex (TSC).
The Epidemiology of LAM
Lymphangioleiomyomatosis is a rare disease that occurs almost exclusively in women. It is estimated that for every million women, three - five will have LAM. 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 35 years old. The reported age range is quite large and LAM has been newly diagnosed in post-menopausal women. Most women with LAM have had symptoms for several years before ultimately being diagnosed.
How is LAM diagnosed?
Lymphangioleiomyomatosis 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 many 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 high resolution chest CT scans can detect the characteristic cystic structure of LAM, thus providing an accurate diagnosis especially if other manifestations of the disease (e.g., benign kidney tumor, lung collapse, or fluid in the lungs) are present. A blood test for vascular endothelial growth factor D (VEGF-D) can sometimes be helpful in diagnosing LAM. In some circumstances, a lung biopsy may be needed to provide an accurate diagnosis.
How LAM Affects the Lungs
When you breathe, oxygen passes through the airways to tiny airsacks (alveoli) in the lungs where oxygen transfers into the blood through a network of tiny blood vessels called capillaries. The abnormal smooth muscle cells of LAM cause blockage of the small airways and release factors causing damage to the lung tissues, resulting in compromise of airflow and oxygen transfer to the blood. Changes to the airways and the lung tissues results in symptoms of shortness of breath, and in some individuals low oxygen levels.
Cysts in the lungs can rupture, allowing air to leak from the lung and into the chest cavity. This condition is called a pneumothorax, and is a common occurrence in women with LAM. As the lung leaks and deflates, it often causes discomfort and shortness of breath.
Some women with LAM will also develop blockage of lymphatic channels from LAM cells, resulting in abnormal fluid collections in the chest and abdomen.
The Course of LAM
LAM is a progressive disease but its progression is usually slow. In some women, however, the disease progresses at a rapid rate. Doctors are working to find indicators (biomarkers) that will help determine who will have a more rapid rate of progression and who will progress more slowly. Whether disease progression is slow or rapid, lung function tends to decrease over time. Many LAM patients will, at some point, require oxygen therapy.
The Treatment of LAM
Although great strides have been made in researching the disease, there is no cure for LAM. However, treatment with the drug sirolimus (also known as rapamycin or Rapamune) as well as everolimus (also known as Afinitor) may improve lung function in some women with LAM. Oxygen therapy is required for women with advanced lung disease. Lung transplantation is often considered for very advanced disease. While many women with LAM add several years to their lives through lung transplantation, it is not a cure.