1 Department of Internal Medicine, Division of Pulmonary Medicine and Allergy, Seoul, South Korea.
2 Department of Internal Medicine, Division of Pulmonary and Allergy, Konkuk University School of Medicine, Seoul, South Korea.
3 Division of Gastroenterology and Hepatology, Hanyang University College of Medicine, Seoul, South Korea.
4 Department of Internal Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Hallym University Kangnam Sacred Heart Hospital, Hallym University College of Medicine, Seoul, South Korea. Electronic address: hychoimd@gmail.com.