Bronchitis CAN lead to pneumonia, but it is rare.
More Info: Though bronchitis does not usually lead to pneumonia, in rare cases it can be a complication such as disease caused by influenza virus. [Gantz, 19]
Bronchitis is an inflammation of the bronchi, the air passages leading to the lungs, whereas pneumonia is an inflammation of the lungs. The same infectious agents that cause bronchitis also cause pneumonia. Because the symptoms of each overlap, it is often difficult to distinguish one from the other even for physicians. There are cases where both the airways and the lungs are infected causing a condition known as bronchopneumonia. [Marrie, 102]
Risk Factors for Bronchitis and Pneumonia
Exposure to lung irritants, such as cigarette smoke, puts you at a greater risk for bronchitis and pneumonia. Additional lung irritants can include dust, chemical fumes, grains, and textiles. People with lower resistance are also at a greater risk including previous illness or conditions that compromise the immune system, the elderly, and young children. 
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”Bronchitis: Complications – MayoClinic.com.” Mayo Clinic. N.p., n.d. Web. 5 Apr. 2012. <http://www.mayoclinic.com/health/bronchitis/DS00031/DSECTION=complications>
 Gantz, Nelson Murray. “Acute Bronchitis.” Manual of Clinical Problems in Infectious Disease. 5th ed. Philadephia: Lippincott Williams & Wilkins, 2006. 19. Print.
 Marrie, Thomas J.. “The Pathology of Community-Acquire Pneumonia.” Community-acquired pneumonia. New York: Kluwer Academic / Plenum Publishers, 2001. 102. Print.
 “Bronchitis: Risk factors – MayoClinic.com.” Mayo Clinic. N.p., n.d. Web. 5 Apr. 2012. <http://www.mayoclinic.com/health/bronchitis/DS00031/DSECTION=risk-factors>.