Which condition is characterized by chronic dilation of the bronchi?

Bronchiectasis is defined by the abnormal and permanent dilation of the bronchi, which can result from chronic inflammation or infection of the airways. This condition leads to the weakening of the bronchial walls and causes them to stretch and enlarge, making it difficult for mucus to clear out effectively. As a result, patients may experience symptoms such as chronic cough, sputum production, and recurrent respiratory infections.

The mechanisms behind bronchiectasis typically involve chronic conditions such as cystic fibrosis, bronchial infections, or autoimmune disorders that lead to airway damage. This chronic dilatation of the bronchi creates a cycle of inflammation and infection, which further exacerbates the condition and leads to declining lung function over time.

In contrast, the other conditions mentioned in the choices do not involve the dilation of the bronchi. Emphysema involves the destruction of the alveoli and loss of elastic recoil in the lungs, while myasthenia gravis is a neuromuscular disorder that affects communication between nerves and muscles. Coronary thrombosis refers to the formation of a blood clot in a coronary artery, affecting heart function rather than the respiratory system. Therefore, bronchiectasis is clearly identified as the condition associated with chronic dilation of the bronchi.