In chronic bronchitis, the earliest feature is increased mucus production due to which histologic change?

• A. Goblet cell hyperplasia
• B. Submucosal gland hypertrophy
• C. Alveolar macrophage accumulation
• D. Smooth muscle hypertrophy

Answer: (B)

In chronic bronchitis, the amount of mucus produced is driven mainly by enlargement of the mucus-secreting glands in the airway submucosa. This submucosal gland hypertrophy increases the secretory capacity of the airways, leading to more mucus being produced and expelled. Clinically, this is reflected by an increased Reid index (gland layer thickness relative to the overall airway wall). While goblet cell hyperplasia also contributes to mucus production by increasing surface mucus cells, the submucosal gland enlargement is the dominant early change that accounts for the increased mucus mass. Alveolar macrophage accumulation signals inflammatory response rather than mucus secretion, and smooth muscle hypertrophy is more about airway remodeling and reactivity than directly increasing mucus production.