Lymphangioleiomyomatosis (LAM) is a lung disease caused by the abnormal growth of smooth muscle cells that leads to blockage of the bronchial tubes and lymphatic vessels, and the formation of holes or cysts in the lung. People who have LAM have trouble breathing because it is more difficult to move air in and out of narrowed bronchial tubes. Additionally, the replacement of normal lung tissue with cysts weakens the ability of the lungs to introduce oxygen into the bloodstream, and also makes patients susceptible to developing pneumothoraces (collapsed lung).
Patients with LAM may also develop growths in the kidneys called angiomyolipomas. These are harmless unless they become large, in which case they can cause bleeding.
What causes lymphangioleiomyomatosis?
LAM results from changes in two genes called TSC1 and TSC2. There is a hereditary form of the disease that occurs in patients who have a disease called tuberous sclerosis. There is a second form of LAM that is not associated with tuberous sclerosis, called sporadic LAM. People who have sporadic LAM also have changes in these genes, but the gene mutations are not hereditary and cannot be passed on to children. The reason these gene mutations occur remains a mystery.
Who gets lymphangioleiomyomatosis?
LAM almost exclusively affects women. Women who have the disease are usually diagnosed between the ages of 20 and 40. About 30% of women who have tuberous sclerosis also have LAM.
What are the symptoms of lymphangioleiomyomatosis?
The abnormal growth of smooth muscle cells and cysts in the lungs of patients who have LAM can cause the following symptoms:
How is lymphangioleiomyomatosis diagnosed?
Because symptoms of LAM are similar to those of asthma or bronchitis, many women who have LAM may not realize it right away, or are given the incorrect diagnosis by doctors who are unfamiliar with the disease. Similarly, the cysts in the lung can be misdiagnosed as emphysema.
LAM is usually treated by a pulmonologist, a doctor who specializes in treating lung diseases. It is important that the doctor be familiar with LAM, and diseases that can mimic LAM, in order to appropriately diagnose and treat the problem. The doctor will examine you and ask about your symptoms. The doctor may also order certain tests, including the following:
High-resolution computed tomography (CT) scan: this creates a sharp picture of the lungs to see if the cysts that characterize the disease are present in the lung. This scan can also show if there is any fluid (pleural effusion) around the lungs.
Lung function tests: you breathe into a machine called a spirometer to determine how much air you can inhale and exhale and whether your lungs are functioning normally.
Pulse oximetry: a small instrument is attached to your finger to measure how much oxygen is in your blood.
VEGF-D blood test: This is a blood test to measure the level of a hormone in your body called VEGF-D. If the level is extremely high in a patient who has cysts in the lungs, a diagnosis of LAM can be made without need for a biopsy. However, a normal level does not rule out the possibility of LAM.
Lung biopsy: In some cases, it is necessary to obtain a piece of tissue to examine under the microscope to diagnose LAM or to look for alternative diseases that can look like LAM. This can be done in one of two ways:
Transbronchial biopsy: the doctor inserts a lighted tube called a bronchoscope into the lungs through the trachea (windpipe) to take samples of the lung. This can be done as an outpatient and does not involve surgery.
Video-assisted thoracoscopy: This is a surgical procedure performed under general anesthesia. The surgeon makes small incisions (cuts) in the chest and inserts a lighted tube to look at the lungs. The doctor can also take biopsies of the lung to examine them more closely.
How is lymphangioleiomyomatosis treated?
There is no cure for LAM, but there is now effective treatment to stabilize the disease and prevent it from progressing (getting worse). The drug sirolimus (also known as rapamycin or Rapamune) was recently approved by the FDA and is used in patients who show signs that they have lost lung function as a result of LAM. Sirolimus can also be used to shrink large angiomyolipomas of the kidney.
Other treatments that may be used in some situations include:
Inhaled medications that help improve the flow of air in the lungs
Various procedures to remove fluid from the chest, or to shrink angiomyolipomas
Lung transplant (in severe cases of LAM)
What is the prognosis (outlook) for patients who have lymphangioleiomyomatosis?
Untreated, LAM can be a progressive disease, which means it can get worse over time. With the introduction of sirolimus, the hope is that the disease can be stabilized for the majority of patients (though not all patients respond to the drug). In the past, the prognosis for patients with LAM was poor, but this is no longer true. Currently, more than 90% of patients are alive 10 years after diagnosis.
To help take care of themselves, patients should see their doctors on a regular basis, and try to maintain a healthy lifestyle. Having LAM may cause anxiety and depression as well, so patients should seek emotional support if necessary.
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