From Wikipedia:
Lymphangioleiomyomatosis (LAM) is a rare lung disease that results in a proliferation of disorderly smooth muscle growth (leiomyoma) throughout the lungs, in the bronchioles, alveolar septa, perivascular spaces, and lymphatics, resulting in the obstruction of small airways (leading to pulmonary cyst formation and pneumothorax) and lymphatics (leading to chylous pleural effusion). LAM occurs in a sporadic form, which affects only females, usually of childbearing age; LAM also occurs in patients who have tuberous sclerosis.
From the Stanford Online Report:
LAM is a relentless and often fatal disease that ravages the lungs of young and middle-aged women. In normal lungs, a sheath of smooth muscle cells surrounds the airways and, by contracting or relaxing, regulates air flow to match the body’s need for oxygen. But in LAM patients, over years the smooth muscle cells begin to multiply uncontrollably. Bundles of cells can narrow the airways and block blood and lymph vessels, causing difficulty breathing, internal bleeding and fluid buildup. Proliferating muscle can pinch off the small air sacs known as alveoli, which can then form air-filled cysts. Cysts near the surface of the lungs — known as blebs — can rupture and cause a partial or complete collapse of the lung.
From The LAM Foundation:
Lymphangioleiomyomatosis (LAM) is a rare lung disease that was first described in the medical literature by von Stossel in 1937. The disease is characterized by an unusual type of muscle cell that invades the tissue of the lungs, including the airways, and blood and lymph vessels. Over time, these muscle cells form into bundles and grow into the walls of the airways, and blood and lymph vessels, causing them to become obstructed.
Lymphangioleiomyomatosis is pronounced lim-fan je-o-lio-mi o-ma-to sis. Lymph and angio refer to the lymph and blood vessels. Leiomyomatosis refers to the formation of the bundles of the unusual muscle cells.