Lymphangioleiomyomatosis (LAM) is a diffuse cystic lung disease caused by bronchiolar obstruction and lung destruction due to proliferation of immature smooth muscle cells in small vessels, lymphatics and bronchioles.

Almost all cases occur in females in childbearing age. About 1% of patients with tuberous sclerosis have lung disease similar to LAM.

Differential diagnosis includes:

• Langerhans cell histiocytosis (LCH): cysts tend to occur in upper lobes
• lymphocytic interstitial pneumonia: cysts associated with fibrosis
• cystic bronchiectasis:characterized by saccular dilatation of bronhi extending to pleura