Pathology
Respiratory System
Respiratory pathology for MBBS and NEET-PG: pneumonia, lung abscess, COPD, bronchiectasis, tuberculosis, occupational lung disease and bronchogenic carcinoma, mapped to NMC codes PA26.1 to PA26.7.
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Respiratory System
Respiratory pathology for MBBS and NEET-PG: pneumonia, lung abscess, COPD, bronchiectasis, tuberculosis, occupational lung disease and bronchogenic carcinoma, mapped to NMC codes PA26.1 to PA26.7.
This chapter covers respiratory pathology. It includes pneumonia and lung abscess, obstructive airway disease and bronchiectasis, pulmonary tuberculosis, occupational lung diseases, and bronchogenic carcinoma, with the morphological features that examiners commonly test.
High-yield: Respiratory System
- Lobar pneumonia passes through congestion, red hepatisation, grey hepatisation and resolution, most often caused by Streptococcus pneumoniae.
- Bronchopneumonia is a patchy consolidation centred on bronchi, common at the extremes of age.
- A lung abscess is a localised collection of pus, often from aspiration, and shows a fluid level on a chest radiograph.
- Chronic obstructive pulmonary disease comprises chronic bronchitis and emphysema, strongly linked to smoking.
- Chronic bronchitis is defined clinically by a productive cough for at least three months in two consecutive years.
- Emphysema is permanent enlargement of the air spaces distal to the terminal bronchiole with wall destruction.
- Centriacinar emphysema is linked to smoking; panacinar emphysema is linked to alpha-1 antitrypsin deficiency.
- Bronchiectasis is permanent dilatation of bronchi from chronic infection and obstruction, producing copious sputum.
- Primary tuberculosis forms a Ghon focus with hilar node involvement, together called the Ghon complex.
- Secondary (reactivation) tuberculosis typically affects the lung apices and can cavitate.
- Silicosis shows whorled collagenous nodules and predisposes to tuberculosis; asbestosis causes ferruginous bodies and mesothelioma.
- Bronchogenic carcinoma is the leading cause of cancer death, with squamous cell and small cell types linked to smoking.
- Small cell lung carcinoma is central, aggressive and associated with paraneoplastic syndromes such as SIADH and ectopic ACTH.
- A pleural effusion is transudative (heart failure) or exudative (infection, malignancy), separated by Light criteria.
Obstructive lung disease essentials
- **Chronic bronchitis:** Productive cough three months a year for two years; mucous gland hyperplasia.
- **Emphysema:** Air space enlargement with wall destruction; centriacinar (smoking) or panacinar (alpha-1 antitrypsin).
- **Bronchiectasis:** Permanent bronchial dilatation from chronic infection; copious sputum.
- **Lung cancer:** Small cell (central, paraneoplastic) and squamous cell (central, hypercalcaemia) linked to smoking.
NMC competencies in this chapter
- **PA26.1:** Aetiology, types, pathogenesis, morphology and complications of pneumonia
- **PA26.2:** Aetiology, morphology and complications of lung abscess
- **PA26.3:** Obstructive airway disease and bronchiectasis
- **PA26.4:** Aetiology, pathogenesis, morphology and complications of tuberculosis
- **PA26.5:** Occupational lung disease: exposure, pathogenesis and complications
- **PA26.6:** Pleural effusions: transudate versus exudate
- **PA26.7:** Integrated approach to respiratory pathology and lung tumours
Frequently Asked Questions
What are the stages of lobar pneumonia?
Congestion, red hepatisation, grey hepatisation and resolution, usually caused by Streptococcus pneumoniae.
How do chronic bronchitis and emphysema differ?
Chronic bronchitis is defined clinically by a chronic productive cough with mucous gland hyperplasia, while emphysema is permanent air space enlargement with alveolar wall destruction.
What is the Ghon complex?
The combination of a peripheral Ghon focus in the lung and its draining hilar lymph node involvement, seen in primary tuberculosis.
Why is small cell lung cancer important?
Because it is central, highly aggressive and associated with paraneoplastic syndromes such as SIADH and ectopic ACTH secretion.
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