Pulmonary lymphangioleiomyomatosis (LAM), a rare progressive lung disease affecting primarily women of childbearing age that is characterized by cyst rapture, chylothorax from obstruction of lymphatics, and progressive decline of pulmonary function, has also been associated with inactivating mutations and loss of function of TSC2 that lead to uncontrolled mTORC1 activation and cell growth [3–6]. The gene discussed is TSC2; the disease is lymphangioleiomyomatosis.