BACKGROUND Common Variable Immunodeficiency (CVID) is one of the most clinically important primary immunodeficiencies due to its frequency, serious complications, and long-term costs of therapy. A form of lung disease known as granulomatous and lymphocytic interstitial lung disease (GLILD) occurs in 10-15% of patients with CVID. The causes of GLILD are unknown; no long-term study has defined the natural course of GLILD; and no clinical trials have been done to define the best possible treatment for this condition. As a result, currently there is no proven standard of care for the treatment of GLILD.