What manifestation is characteristic only to emphysema?

Barrel chest is a characteristic manifestation specifically associated with emphysema, a type of chronic obstructive pulmonary disease (COPD). In emphysema, the destruction of the alveoli and the loss of elastic recoil lead to hyperinflation of the lungs. This hyperinflation results in an increased anterior-posterior diameter of the thoracic cage, creating the barrel-shaped appearance. This physical change is a distinct hallmark of emphysema and is often observed during a physical examination.

Other symptoms, while common in emphysema, are not exclusive to it. Morning cough is frequently associated with chronic bronchitis, dyspnea on exertion can be seen in various respiratory conditions, and excessive sputum production is primarily related to chronic bronchitis. Thus, while these manifestations may occur in emphysema patients, they are not unique to this condition, making barrel chest the only exclusive characteristic of emphysema.