Lymphangioleiomyomatosis (LAM) is a rare disease categorized by an overgrowth of atypical smooth muscle cells (LAM cells) in the lungs and axial lymphatics, which is associated with the mesenchymal tumor angiomyolipoma. The disease occurs in women generally in their mid thirties with a prevalence approximately 1 per million in the general population but is much more frequent in women with tuberous sclerosis complex (TSC). LAM is categorized by airflow obstruction, lung cysts, recurrent pneumothorax, and pleural and abdominal chylous collections. The disease is progressive, generally resulting in respiratory failure and death. The TSC-2 gene is abnormal in LAM cells and may be responsible for their disordered growth. These cells are of an unusual phenotype, expressing smooth muscle proteins, melanoma proteins, estrogen and progesterone receptors. Although at present of unknown significance these are useful in diagnosis. Treatment is largely supportive, being directed at airflow obstruction, pneumothorax, chylous complications, and bleeding from angiomyolipomas. In patients with rapidly progressive disease, hormone manipulation is frequently tried in the form of progesterone or antiestrogen therapies although no firm evidence of their efficacy exists.