General Information about LAM
What is LAM? Lymphangioleiomyomatosis is a rare disease that primarily affects women of childbearing age. An unusual type of muscle cell grows throughout the lungs, causing obstruction of airways, lymph vessels and blood vessels, preventing the lungs from providing oxygen to the body. Although classified as an interstitial lung disease, it is more like emphysema, with airway obstruction and formation of cysts. LAM occurs in two forms, sporadically, and associated with tuberous sclerosis complex (TSC), a distinct syndrome that also affects the central nervous system, eyes and skin.
What are the symptoms? Progressive difficulty breathing, sometimes with a cough. Pneumothorax, partial collapse of a lung due to cyst rupture and leakage of air from the lung into the surrounding chest, is often the first event leading to diagnosis. Symptoms of pneumothorax are sudden shortness of breath and chest discomfort.
How serious is LAM? LAM is debilitating and life-threatening, eventually causing respiratory failure. Early on, most people can live normally. Lung function gradually worsens, at an unpredictable rate. Physical activity becomes limited, and oxygen is required. There can be repeated pneumothoraces. Due to blockage or rupture of lymph vessels, fluid can leak into the chest cavity (chylous pleural effusions), causing more breathlessness. People with LAM typically live 8-10 years after diagnosis, with reports of 20-year survival.
How is LAM diagnosed? Over half have airflow obstruction on pulmonary function tests; most have impaired oxygen exchange between the lungs and blood. Chest X-rays may be normal when cysts are small, or show over-inflation of the lungs. LAM can be mistaken for asthma or COPD. As disease progresses, opacities can be seen, and lymph nodes may be enlarged. Thin-walled cysts throughout the lungs on high-resolution CT scans can be diagnostic. Tissue samples are sometimes obtained for confirmation, by bronchoscopy, video-assisted thoracoscopic or open lung biopsy.
Are other areas of the body affected by LAM? Benign masses of blood vessels, lymphatic material, muscle tissue and fat are often seen in the kidneys, abdomen, retroperitoneal space and pelvis. Symptoms include bloating, abdominal pain and leg edema.
What causes LAM? Unknown. There is evidence for gene mutations, possibly in combination with environmental factors. Loss of cellular tumor suppression functions may contribute.
Who is at risk? LAM almost exclusively afflicts women of childbearing age. Post-menopausal women can be affected, especially if taking estrogen; it is rarely seen in men. In the National Heart, Lung and Blood Institute (NHLBI) LAM registry, the average age of symptom onset was 37, with diagnosis at 41. Caucasians are at highest risk, with lower rates among Asians and those of African descent. LAM occurs in a third of people with tuberous sclerosis, often at a younger age and with less impaired lung function.
How common is LAM? 1,300 known people with LAM in North America. Based on TSC prevalence, 8,000-10,000 women probably have cystic lesions consistent with LAM, and over 250,000 worldwide.
Can LAM be prevented? No. Earlier diagnosis, including screening people with TSC, may improve outcomes, through avoidance of tobacco smoke and estrogen-containing medications, and the potential for early treatment. Women are cautioned to avoid pregnancy, since there can be disease acceleration. Due to increased risk of pneumothorax, air travel should be avoided if there is new or worsening breathlessness or chest pain, prior pneumothorax or coughing up blood, or multiple cysts in the lung periphery.
How is LAM treated? There is not yet a cure. Symptoms may improve with inhaled bronchodilators, such as ipratropium or albuterol, and oxygen is needed for advanced disease. Estrogen probably plays a central role in disease progression, and some respond to hormonal manipulation. While taking sirolimus, which affects cell growth and proliferation, participants in early trials showed improved quality of life, activity level and lung function. Sirolimus has long-term adverse effects, and research is necessary to determine optimal dosing and timing of therapy, and those likely to benefit. Lung transplant provides overall relief, although with a high complication rate.Source: Dona Upson, MD, Chair , ATS Council of Chapter Representatives (CCR)
Four Facts About LAM