Lymphangioleiomyomatosis (LAM) is a disease caused by the abnormal growth of specific muscle cells known as smooth muscle cells within certain organs. This disease can cause progressive shortness of breath by destroying lung tissue and, in some patients, by causing accumulation of fluid around the lung known as pleural effusion. These effusions occur when normal removal of this fluid is blocked. The disease can also block the drainage of fluid in the abdomen, which causes ascites, and can cause abnormal growths that impair kidney function.