Evaluating the Long-term Safety and Tolerability of Imatinib in Patients With Lymphangioleiomyomatosis (LAM)

Participants will take Imatinib mesylate (imatinib), an FDA approved drug for leukemia, orally 400 mg (twice daily)

Placebo will be administered in the same dosage and manner as the study drug. The placebo looks like the study drug but contains no active ingredients.