Indeed, doxycycline treatment for 12 months reduced both urinary MMP-9 and serum MMP-2 levels in LAM patients, but FEV1 (forced expiratory volume in the 1st second) was stabilized or increased only in patients with mild spirometric abnormalities but not in patients with advanced disease [26]. This evidence concerns the gene MMP9 and lymphangioleiomyomatosis.