Bronchitis - acute and chronic. Bronchiolitis. Pathomorphology
Acute bronchitis
Also known as a chest cold, this is the inflammation of the bronchi of the lungs. Common symptoms include cough, mucus, wheezing & fever. The cough may persist for a number of weeks after the initial infection, itself lasting about a week. It is notable that the cough often occurs on expiration. Bronchitis caused by adenoviridae may also cause GI symptoms.
More than 90% of cases are viral (rhinovirus, influenza etc), with RF including smoke, dust and air pollution. Bacterial cases are due to Mycoplasma pneumoniae or Bordetella pertussis.
Damage caused by irritation of the airways leads to inflammation and neutrophils infiltrating tissue, this causes mucosal hypersecretion from goblet cells which can cause obstructive symptoms.
Normal vs inflamed bronchus: the inflamed wall is thickened and swollen, and mucus narrows the lumen.
Image: “Bronchitis” by BruceBlaus, CC BY-SA 4.0, via Wikimedia Commons.
Diagnosis is generally clinical, chest X-ray can rule out pneumonia, sputum sample shows neutrophil granulocytes and a pathogenic microorganism. Treatment is generally not required, the condition is self limiting.
GP NOTEBOOK SAYS:
There is some evidence that ABs have a slight beneficial benefit in treatment of uncomplicated care, but it is minimal. Guidelines suggest not ABs if no comorbidity, consider 7 day delayed AB with advice, noting that symptom resolution can take 3 weeks or more!
If patient requires ABs, a five-day course of amoxicillin (500mg three times a day).
Chronic bronchitis
Most common among smokers and those in highly polluted cities. Diagnosis based on clinical grounds; presence of persistent productive cough for at least 3 months in at least 2 consecutive years.
The key pathogenic feature of chronic bronchitis is hypersecretion of mucus in the bronchi caused by hypertrophy of the submucosal glands in the trachea and bronchi, and goblet cell metaplasia. This is due to chronic irritation of the airways by inhaled substances. The mucous plugging that then occurs in the bronchial lumen help to provide a place for bacteria and viruses to take root and cause an inflammatory response. Irritation of the bronchi causes infiltration of CD8+ lymphocytes, macrophages and neutrophils into the mucosa, this is in contrast to asthma (a diff dx) where this does not occur.