The diagnosis of chronic bronchitis requires the presence of chronic productive cough for over at least 3 months of the year for 2 successive years. The symptoms in this patient (green productive sputum, fever) suggest that he has an acute infection superimposed on chronic bronchitis (history of cigarette smoking, history of excessive mucus production over many years). Histologically, the mucus-producing glands in the bronchi would show hyperplasia and hyperophy and extend to a greater depth in the bronchial wall, resulting in a higher Reid index (ratio of thickness of mucus gland to thickness of bronchial wall).Although the patient is a smoker and is at increased risk for bronchogenic carcinoma, this is unlikely to be the cause of his symptoms. Hemoptysis and weight loss might also be present if he had cancer. Cystic fibrosis presents earlier in life and may be associated with severe production of mucus, especially if bronchiectasis supervenes. The age of the patient and the relative late onset of disease preclude this diagnosis. This patient may also have emphysema, as chronic bronchitis and emphysema are often coexistent. However, although pure emphysema might cause dyspnea, it would not be associated with a fever or a productive cough. Ref:Tallman T.A. (2011). Chapter 67. Acute Bronchitis and Upper Respiratory Tract Infections. In J.E. Tintinalli, J.S. Stapczynski, D.M. Cline, O.J. Ma, R.K. Cydulka, G.D. Meckler (Eds), Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 7e.