1, infection Infection is the most common cause of bronchiectasis. Tuberculosis, pertussis, and adenovirus pneumonia can cause secondary bronchiectasis. Aspergillus and mycoplasma, as well as pathogens that can cause chronic necrotizing bronchopneumonia, can also cause bronchiectasis. 2. congenital and hereditary diseases The most common hereditary disease causing bronchiectasis is cystic fibrosis. In addition, possibly due to the weak development of connective tissue, Marfon syndrome can also cause bronchiectasis. 3. abnormal cilia Abnormal cilia structure and function is an important cause of bronchiectasis. kartagener syndrome manifests as a triad of visceral translocation, sinusitis and bronchiectasis. The disease is accompanied by abnormal cilia function. 4, immunodeficiency Defects in one or more immunoglobulins can cause bronchiectasis. one or more IgG subclass deficiencies are usually associated with recurrent whistling infections and can cause bronchiectasis. IgA deficiency is not often associated with bronchiectasis, but it can coexist with IgG2 subclass deficiencies and cause recurrent septic infections of the lungs and bronchiectasis. 5, foreign body inhalation The long-term presence of foreign bodies in the airways can lead to chronic obstruction and inflammation, secondary to bronchodilation.