Bronchiectasis is the abnormal enlargement of the bronchi in the lungs and leads to permanent expansion. It usually comes with relaxation, swelling and bending of the respiratory tract. It is an irreversible disease, but it is not contagious.

Causes of bronchiectasis:
1. Respiratory tract injury: Respiratory tract infections, such as viral, bacterial, and fungal infections, gastroesophageal reflux and inhalation of toxic gases may cause respiratory tract damage and results in bronchiectasis.

2. Connective tissue diseases or congenital structural abnormalities: It has the highest correlation with rheumatoid arthritis. Congenital structural abnormalities such as bronchial chondrogenesis can cause bronchiectasis.

3. Immune deficiency: Immune deficiency such as immunoglobulin deficiency, human immunodeficiency virus (HIV) infection can easily cause repeated inflammation, destruction and regeneration of the respiratory tract which leads to structural changes.

4. Intestinal diseases: Inflammatory intestinal diseases, ulcerative colitis, etc.

5. Others: Malignant tumours, complications after organ transplantation, α1-antitrypsin deficiency may cause bronchiectasis.