A pregnant 26-year-old woman developed hemosputum, dyspnea and pneumothorax. Lymphangioleiomyomatosis was suspected based on multiple cystic lesions on chest computed tomography. Additionally, moderate thrombocytopenia occurred during the last trimester. Hyperplasia of megakaryocytes in a bone marrow specimen and a high serum titer of platelet-associated IgG led to a diagnosis of idiopathic thrombocytopenic purpura. High-dose intravenous gammaglobulin promptly restored her platelet count, and the patient successfully gave birth to a healthy baby by cesarean section. After delivery, lymphangioleiomyomatosis was diagnosed by lung biopsy that was obtained during a video-assisted thoracoscopic abscission for recurrent pneumothorax. Underlying lymphangioleiomyomatosis and idiopathic thrombocytopenic purpura may be obviated by pregnancy.