Bronchitis pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Seyedmahdi Pahlavani, M.D. [2]; Nate Michalak, B.A.

Bronchitis Main page

Patient Information

Overview

Causes

Classification

Acute bronchitis
Chronic bronchitis

Differential Diagnosis

## Overview

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Bronchitis is the inflammatory response of the bronchial epithelium to infections or irritants. The pathophysiological findings seen with acute bronchitis include: wall thickening, inflammation, and increased mucus production. When the process becomes chronic, bronchial mucociliary function decreases, leading to airway clogging by debris and copious mucus secretion.

## Pathophysiology

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### Pathogenesis

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* Acute bronchitis:

Inflammatory response of the bronchial epithelium to infectious agents or irritants that involve the medium and large size airways results in thickening of the bronchial and tracheal mucosa.

* Chronic bronchitis:

Hallmark features include: hyperplasia and hypertrophy of the goblet cells of the airway, resulting in an increase in secretion of mucus, which contributes to airway obstruction.

### Microscopy

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* Acute bronchitis caused by influenza virus shows an epithelial-cell desquamation in association with the presence of a lymphocytic cellular infiltrate.[1]
* On microscopic histopathological analysis, chronic bronchitis shows infiltration of the airway walls with inflammatory cells, particularly CD8+ T-lymphocytes and neutrophils.[2] Inflammation is followed by scarring and remodeling that thickens the walls resulting in narrowing of the small airways. Further progression leads to metaplasia and fibrosis of the lower airway. The consequence of these changes is a limitation of airflow.[3][4][5]

## References

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1. ↑ WALSH JJ, DIETLEIN LF, LOW FN, BURCH GE, MOGABGAB WJ (1961). "Bronchotracheal response in human influenza. Type A, Asian strain, as studied by light and electron microscopic examination of bronchoscopic biopsies". Arch. Intern. Med. 108: 376–88. PMID 13782910.
2. ↑ Baraldo S, Turato G, Badin C, Bazzan E, Beghé B, Zuin R, Calabrese F, Casoni G, Maestrelli P, Papi A, Fabbri LM, Saetta M (2004). "Neutrophilic infiltration within the airway smooth muscle in patients with COPD". Thorax. 59 (4): 308–12. PMC 1763819. PMID 15047950.
3. ↑ Cosio MG, Saetta M, Agusti A (2009). "Immunologic aspects of chronic obstructive pulmonary disease". N. Engl. J. Med. 360 (23): 2445–54. doi:10.1056/NEJMra0804752. PMID 19494220.
4. ↑ Kumar P, Clark M (2005). Clinical Medicine, 6ed. Elsevier Saunders. pp 900-901. ISBN 0702027634.
5. ↑ McDonough JE, Yuan R, Suzuki M, Seyednejad N, Elliott WM, Sanchez PG, Wright AC, Gefter WB, Litzky L, Coxson HO, Paré PD, Sin DD, Pierce RA, Woods JC, McWilliams AM, Mayo JR, Lam SC, Cooper JD, Hogg JC (2011). "Small-airway obstruction and emphysema in chronic obstructive pulmonary disease". N. Engl. J. Med. 365 (17): 1567–75. doi:10.1056/NEJMoa1106955. PMC 3238466. PMID 22029978.

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