MBL2 and pneumothorax: Other less common underlying conditions included pulmonary sarcoidosis (13, 9%), gamma interferon deficiency (12, 8%), previous pneumothorax (13, 9%), mannose binding lectin deficiency (10, 7%), survivors of lung cancer (7, 5%), rheumatoid arthritis (4, 3%), and impaired 1L-17 production (2, 1%).