NORD gratefully acknowledges the members of the Scientific Advisory Board of the LAM Foundation for assistance in the preparation of this report and Joel Moss, MD, PhD at the National Heart, Lung, and Blood Insitute, National Institutes of Health, for reviewing this report.
Lymphangioleiomyomatosis (LAM) is a rare progressive multisystem disorder that predominantly affects women of childbearing age. It occurs in women who have tuberous sclerosis, and also in women who do not have a heritable genetic disorder. LAM is characterized by the spread and uncontrolled growth (proliferation) of specialized cells (smooth muscle-like LAM cells) in certain organs of the body, especially the lungs, kidney and lymphatics. Common symptoms associated with LAM include coughing and/or difficulty breathing (dyspnea), especially following periods of exercise or exertion. Affected individuals may also experience complications including collapse of a lung or fluid accumulation around the lungs (pleural effusion). The disorder is progressive and, in some cases, may result in chronic respiratory failure.
The symptoms of LAM vary from case to case. Specific symptoms depend upon which organs are affected by the LAM cells. In most cases, the initial symptoms involve the lung and include shortness of breath, especially upon exercise or exertion. Affected individuals may also experience episodes of chest pain, coughing, wheezing, and coughing up small amounts of blood (hemoptysis).
Some individuals may experience fluid (e.g. chyle) accumulation in the chest cavity around the lungs (pleural effusion). Chyle is a fat-laden cloudy fluid that is absorbed during digestion by the lymphatic vessels located around the intestine. Chyle normally flows through lymphatic vessels into the upper chest (thoracic duct) and is then deposited into veins, where it mixes with blood. In some people with LAM, the lymphatic vessels may rupture or become blocked (obstructed), causing chyle to accumulate in the chest cavity (chylothorax). In some cases, chyle may accumulate in the abdomen causing an increase in girth, a condition called chylous ascites. Involvement of the axial lympatics may also lead to formation fo lymphangioleiomyomas, chyle- filled lymphatic structures within the chest and abdomen.
Some individuals with LAM may experience collapse of a lung that is unrelated to trauma (spontaneous pneumothorax). The symptoms of a collapsed lung may include sudden, sharp chest pain; difficult, rapid breathing; rapid heartbeat (tachycardia); low blood pressure (hypotension); profuse sweating (diaphoresis); dizziness; and/or lack of normal chest movement on the affected side of the chest. A collapsed lung may recur in some individuals.
Approximately 50 percent of individuals with LAM develop angiomyolipomas, which are benign tumors made up of fat, blood vessels and smooth muscle like cells. These tumors affect the kidneys or abdomen and often do not cause symptoms (asymptomatic). In some cases, they may cause flank pain, blood in the urine (hematuria) or bleeding into the abdomen (abdominal hemorrhaging).
Symptoms of LAM may become progressively worse as LAM cell proliferation continues, eventually resulting in chronic life-threatening respiratory failure. The symptoms of LAM often worsen during pregnancy. Many cases of LAM are associated with osteoporosis, a condition characterized by progressive thinning of the bones.
The exact cause of LAM is not known. Since the disease occurs almost exclusively in females of reproductive age, it is possible that an association exists between female hormones (i.e., estrogen and progesterone) and LAM.
Some researchers are studying the connection between a rare genetic disorder known as tuberous sclerosis complex (TSC) and LAM. Approximately 30 percent of women with TSC show evidence of pulmonary lymphangioleiomyomatosis, suggesting that these disorders may share a common cause or origin. TSC is caused by mutations in one of two genes known as the TSC1 gene or TSC2 gene.
Recently, studies have shown that some individuals with LAM who do not have TSC have somatic mutations (e.g., mutations that occur in peripheral tissues after conception) in the TSC2 gene. These mutations were not found in the blood or the normal lung or normal kidney cells of affected individuals. These data suggest that TSC mutations are a cause of LAM even in women who do not have the heritable disorder, TSC.
The symptoms associated with LAM occur due to the spread and accumulation (proliferation) of LAM cells into various organs of the body, especially the lungs. This abnormal proliferation results in the formation of cysts as well as the obstruction of affected airways (breathing tubes), blood vessels, and lymph vessels. Infiltration of the lung with LAM cells may result in progressive breathing difficulties, lung collapse, and interference with the lung’s ability to deliver oxygen to the rest of the body.
Obstruction of blood vessels may result in bleeding in the lungs (pulmonary hemorrhage) and coughing up of blood (hemoptysis). Obstruction of lymph vessels may result in chylous effusions and ascites. Lymph vessels are part of the lymphatic system, a circulatory network of vessels, ducts, and nodes that filter and distribute lymph and blood cells throughout the body. Lymph is a fluid that circulates through the body cleaning and strengthening tissue. After performing its functions, lymph is drained away through the lymphatic system.
LAM is a rare disorder that predominantly affects women of childbearing age. The average age of affected individuals at symptom onset is 33. More than 400 cases have been reported in the United States in the medical literature since Dr. Von Stossel first described the disorder in 1937. Some estimates suggest that more than 1,000 women in the United States may have LAM. Many researchers believe that the disorder in under-diagnosed, making it difficult to determine its true frequency in the general population. The Tuberous Sclerosis Association recommends that women with tuberous sclerosis should be screened for LAM at least once on reaching maturity.
The diagnosis of LAM may be confirmed by a thorough clinical evaluation that includes a detailed patient history and a variety of specialized tests including radiographic (x-ray) studies, lung function tests, and/or surgical removal and microscopic study of affected tissue (biopsy). In about 80 percent of people with LAM, CT studies reveal cysts in the lungs in or around one or both lungs (pleural effusion). CT studies of the abdomen may reveal angiomyolipomas or lymphangioleiomyomas that support a diagnosis of LAM.
Surgical open lung biopsy is one definitive way to confirm the diagnosis of LAM. These biopsy tissue samples verify the presence of LAM cells.
The treatment of LAM is directed toward the specific symptoms that are apparent in each individual. Fluid accumulation in the lungs (pleural effusion) may be drained by means of a surgically implanted shunt or tube. The surgical insertion of a sterile irritant (such as the antibiotic oxycycline) into the space surrounding the lungs can help to fuse the lung to the chest wall and reduce fluid accumulation around the lungs. Drugs that temporarily widen the bronchial tubes (bronchodilators) may help to alleviate breathing difficulties (asthma-like symptoms) in some cases. Supplemental oxygen should be administered as needed.
Rapamune (sirolimus) has been approved to treat lymphangioleiomyomatosis (LAM), a rare progressive lung disease that primarily affects women of childbearing age. Rapamune is manufactured by Wyeth Pharmaceuticals, Inc., a subsidiary of Pfizer, Inc.
Because LAM occurs most often in young women of childbearing age, researchers have speculated that female hormones such as estrogen play a role in the development of the disorder. A link between LAM and female hormones has not been proven. However, many physicians have explored the use of agents that lower the production or effects of estrogen in the body. The results have varied greatly among individuals. Such agents may include medroxyprogesterone acetate. Some affected individuals have experienced symptomatic improvement while on this medication, especially those with recurrent chylous lung effusions, but routine use is not recommended because of significiant side effects. Estrogen-containing medications and dietary supplements should be discontinued in patients with LAM.
A fat replacement diet may or may not be beneficial for some women with chylothorax associated with LAM. Surgical removal of abdominal angiomyolipomas may be necessary in cases where these growths cause bleeding and pain. The initial recommendation is for the angiomyolipoma to be embolized, a procedure that may lead to necrosis of the lesion.
In individuals with severe cases of LAM, lung transplantation may be considered as a last resort. Other treatment is symptomatic and supportive.
Because of the frequent association of LAM with osteoporosis, affected individuals should have their bone mineral density tested. Any loss of bone mineral density should be treated with vitamin D and calcium supplementation and bisphosphonates.
Scientists are investigating the role of hormone therapy in the development and onset of LAM. Some researchers have suggested that hormonal response markers (i.e., estrogen and progesterone receptor status) should be measured in lung tissue biopsy samples. It is hoped that, at some point, these studies may help to determine the best course of treatment. Hereditary factors are also being studied to help determine whether or not a genetic predisposition is essential to the development of LAM.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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