# Respiratory System for NEET PG Pathology: Pneumonia, Lung Abscess, COPD, Bronchiectasis, Pneumoconioses, Lung Cancer, Mesothelioma Source: https://tracknation.in/story/respiratory-system-for-neet-pg-pathology-pneumonia-lung-abscess-copd-bronchiectasis-pneumoconioses-lung-cancer-mesothelioma (TrackNation — free UPSC notes with PYQs) > NEET PG Pathology: pneumonia pathogens, lung abscess sites, chronic bronchitis and emphysema, alpha-1 antitrypsin deficiency, asthma, bronchiectasis, silicosis, coal worker pneumoconiosis, asbestosis, byssinosis and berylliosis, lung carcinoma types and Pancoast tumour, and mesothelioma, with a diagram, hooks, vignette MCQs and cards. ## Start Here 🎯 **Exam priority: High.** *Expect: match a dust to its disease, the chronic bronchitis definition, alpha-1 antitrypsin, lung abscess site after aspiration, the commonest lung cancer type, Pancoast/Horner, and asbestos-related pleural disease and mesothelioma.* CBME mapping: **PA 25.1–25.7**. Tuberculosis is in article 7; paraneoplastic syndromes of lung cancer in article 4. *Occupational lung disease, airways and infection, lung cancer and mesothelioma. Drawn by TrackNation.* ## Infection - **Pneumonia**: *Streptococcus pneumoniae* is the commonest pathogen in all ages, settings and regions. Other community-acquired causes: *H. influenzae*, atypicals (*Chlamydia pneumoniae*, *Mycoplasma*, *Legionella*) and viruses. - **Lung abscess**: a pus-filled cavity, usually from aspiration of oral secretions; anaerobes dominate. It forms in segments that are dependent when lying down — posterior segments of the upper lobes, superior or lateral basal segments of the lower lobes — with an air-fluid level. - **Acute hypoxaemic respiratory failure**: PaO2 < 60 mm Hg, PaO2/FiO2 < 300 or SpO2 < 88%. ## Obstructive Airway Disease - **COPD** = chronic obstructive bronchitis and/or emphysema. Smoking is the main cause, yet only about 15% of smokers develop clinical COPD. **Chronic bronchitis**: productive cough on most days for at least 3 months a year for 2 consecutive years. - **Alpha-1 antitrypsin deficiency**: unchecked proteases destroy lung tissue (emphysema in adults); abnormal protein stuck in the liver causes liver disease. A cause of COPD in non-smokers. - **Asthma**: bronchoconstriction, airway oedema and inflammation, hyperreactivity and remodelling, driven by Th2 cells, eosinophils and mast cells. - **Bronchiectasis**: permanent dilation and destruction of large bronchi from chronic infection — cystic fibrosis, immune defects, primary ciliary dyskinesia; chronic cough with purulent sputum. ## Occupational Lung Disease - **Silicosis** (crystalline silica): nodular fibrosis, upper-lobe 1–3 mm nodules, eggshell-calcified hilar nodes; higher risk of TB, COPD and lung cancer. - **Coal worker pneumoconiosis**: from mild disease to progressive massive fibrosis; with rheumatoid arthritis → Caplan syndrome (rheumatoid nodules). - **Asbestosis**: peripheral lower-lobe fibrosis; asbestos bodies support (but are not needed for) diagnosis. Asbestos pleural disease: plaques, calcification, thickening, effusion and **mesothelioma** (latency 30–50 years). - **Byssinosis**: cotton, flax and hemp dust (endotoxin) — chest tightness worst on the first working day of the week. **Chronic beryllium disease**: granulomas that mimic sarcoidosis. ## Lung Cancer - The leading cause of cancer death worldwide; about 85% linked to smoking, but 15–20% of patients never or barely smoked. Risk falls after quitting but never returns to baseline. Radon is the second cause in the US; asbestos, arsenic and other carcinogens add risk. - Small cell vs non-small cell. **Adenocarcinoma** is the commonest subtype, especially in never-smokers; targetable drivers (EGFR, ALK) are mostly found here. Squamous cell carcinoma carries TP53 mutations in about 91%. - **Pancoast (superior sulcus) tumour**: invades brachial plexus, pleura or ribs → shoulder and arm pain, hand weakness, and **Horner syndrome** (ptosis, miosis, anhidrosis) when the sympathetic chain is involved. Small cell paraneoplastic syndromes: article 4. ## Traps the Examiner Sets - Silicosis = upper lobes + TB risk; asbestosis = lower lobes + pleural plaques + mesothelioma. - Byssinosis = "Monday" chest tightness. - Adenocarcinoma = commonest and the type in non-smokers. - Aspiration abscess: dependent segments, anaerobes. ## Memory Hooks & Shortcuts *Shortcuts to lock in this article's numbers and lists. Each one only re-packages facts proven above.* - 🧠 **Silica Settles Up (upper lobes) and Summons TB** — silicosis - 🧠 **Asbestos goes to the Abdomen-end (lower lobes) and the pleura** — asbestosis - 🧠 **Byssinosis = Blue Monday** — byssinosis timing - 🧠 **Adeno for the Abstainers (non-smokers)** — adenocarcinoma - 🧠 **Pancoast Pinches the sympathetic chain → Ptosis, Pupil small** — Pancoast and Horner - 🧠 **3 months × 2 years = chronic bronchitis** — definition ## Rapid-Revision Cards - S. pneumoniae — all ages, settings, regions. - Mycoplasma, Chlamydia pneumoniae, Legionella. - Aspiration; anaerobes; dependent segments; air-fluid level. - Cough ≥ 3 months/yr × 2 yr. - Only ~15%. - Emphysema + liver disease; non-smokers. - Th2, eosinophils, mast cells. - Dilated bronchi; CF, immune defects, PCD. - PaO2 < 60, P/F < 300, SpO2 < 88%. - Upper lobes, eggshell nodes, TB risk. - Pneumoconiosis + RA nodules. - Lower lobes, pleural plaques, asbestos bodies. - Asbestos; latency 30–50 yr. - Cotton/flax/hemp; Monday tightness. - Granulomas like sarcoid. - ~85%; 15–20% never smoked. - Adenocarcinoma (never-smokers too). - Shoulder/arm pain, Horner syndrome. - 2nd cause of lung cancer (US). ## Sources *Facts in this article were checked against these documents.* - MSD Manual Professional: Pneumonia; Lung Abscess; COPD; Alpha-1 Antitrypsin Deficiency; Asthma; Bronchiectasis; Acute Hypoxemic Respiratory Failure — Merck & Co. (MSD Manuals), reviewed 2025–26 (link) - MSD Manual Professional: Silicosis; Coal Worker Pneumoconiosis; Asbestosis; Asbestos-Related Pleural Disease; Mesothelioma; Byssinosis; Beryllium Disease — Merck & Co. (MSD Manuals), reviewed 2026 (link) - MSD Manual Professional: Lung Carcinoma — Merck & Co. (MSD Manuals), reviewed 2026 (link) - Competency Based Undergraduate Curriculum, Pathology (PA 25) — National Medical Commission, 2024 ## Test Yourself: Practice Questions Thirty questions in NEET PG style, most of them clinical vignettes. ## Practice Questions (NEET PG pattern) *Original questions written in the style of the exam: +4 for a correct answer, −1 for a wrong one. Every answer was checked against the sources listed above. NEET PG papers are not published by NBEMS, so these are not past-paper questions.* **Q1.** The commonest bacterial cause of pneumonia across all age groups and settings is - (a) Streptococcus pneumoniae - (b) Staphylococcus aureus - (c) Klebsiella - (d) Pseudomonas **Answer: (a)** — Its incidence is falling in some countries. **Q2.** Which of these is an 'atypical' cause of community-acquired pneumonia? - (a) Streptococcus pneumoniae - (b) Escherichia coli - (c) Haemophilus influenzae - (d) Mycoplasma pneumoniae **Answer: (d)** — Also Chlamydia pneumoniae and Legionella. **Q3.** A patient at risk of aspiration develops a lung cavity with an air-fluid level. The usual organisms and the cause are - (a) a pulmonary infarct - (b) fungal infection - (c) TB reactivation - (d) anaerobes after aspiration of oral secretions **Answer: (d)** — Often mixed anaerobes and aerobes. **Q4.** An aspiration lung abscess in a recumbent patient typically forms in the - (a) posterior segments of the upper lobes or superior/lateral basal segments of the lower lobes - (b) anterior segment of the upper lobe only - (c) lingula only - (d) apex only **Answer: (a)** — The dependent segments. **Q5.** Chronic bronchitis is defined clinically as productive cough on most days for at least - (a) 6 weeks once - (b) 1 year continuously - (c) 1 month a year - (d) 3 months a year for 2 consecutive years **Answer: (d)** — Emphysema is defined pathologically or radiologically. **Q6.** Of people who smoke, the share who develop clinically apparent COPD is about - (a) 90% - (b) 50% - (c) 15% - (d) 1% **Answer: (c)** — Smoking is still the main risk factor. **Q7.** A non-smoker has emphysema and liver disease. The likely inherited cause is - (a) alpha-1 antitrypsin deficiency - (b) Marfan syndrome - (c) cystic fibrosis - (d) Kartagener syndrome **Answer: (a)** — Unopposed proteases destroy lung; abnormal protein accumulates in the liver. **Q8.** The cells that drive allergic (T2-high) asthma include - (a) plasma cells only - (b) neutrophils only - (c) NK cells only - (d) Th2 lymphocytes, eosinophils and mast cells **Answer: (d)** — With airway remodelling over time. **Q9.** A young adult has chronic cough with large amounts of purulent sputum; CT shows dilated, thick-walled bronchi. A common underlying cause is - (a) asthma - (b) pulmonary embolism - (c) cystic fibrosis - (d) sarcoidosis **Answer: (c)** — Also immune defects, recurrent infection and primary ciliary dyskinesia. **Q10.** Bronchiectasis can result from a congenital defect in mucociliary clearance called - (a) alpha-1 antitrypsin deficiency - (b) surfactant deficiency - (c) primary ciliary dyskinesia - (d) sickle cell disease **Answer: (c)** — About 3% of previously 'idiopathic' cases. **Q11.** Acute hypoxaemic respiratory failure is defined by - (a) pH < 7.35 only - (b) PaCO2 > 50 only - (c) PaO2 < 60 mm Hg, PaO2/FiO2 < 300 or SpO2 < 88% - (d) SpO2 < 95% **Answer: (c)** — From shunting and V/Q mismatch. **Q12.** A worker with years of dust exposure has upper-lobe nodular opacities and eggshell calcification of hilar nodes. The disease and a key complication are - (a) asbestosis — mesothelioma - (b) byssinosis — asthma - (c) berylliosis — sarcoid - (d) silicosis — increased tuberculosis risk **Answer: (d)** — Also COPD and lung cancer. **Q13.** Silicosis is caused by inhaling - (a) respirable crystalline silica - (b) beryllium fumes - (c) asbestos fibres - (d) cotton dust **Answer: (a)** — Nodular pulmonary fibrosis. **Q14.** A coal miner with rheumatoid arthritis develops multiple lung nodules. This is - (a) TB - (b) Caplan syndrome (rheumatoid pneumoconiosis) - (c) silicosis - (d) metastatic cancer always **Answer: (b)** — Must be distinguished from cancer and infection. **Q15.** A worker has bilateral peripheral lower-lobe fibrosis and calcified pleural plaques. The likely exposure is - (a) asbestos - (b) cotton - (c) coal - (d) silica **Answer: (a)** — Asbestos bodies support the diagnosis. **Q16.** The hallmark of asbestos exposure in the pleura is - (a) pleural plaques (often calcified) - (b) pneumothorax - (c) chylothorax - (d) empyema **Answer: (a)** — Also thickening, effusion and mesothelioma. **Q17.** A man develops a primary pleural cancer decades after occupational mineral-fibre exposure. The tumour and typical latency are - (a) lymphoma — 5 years - (b) sarcoma — 6 months - (c) mesothelioma — 30 to 50 years - (d) adenocarcinoma — 1 year **Answer: (c)** — Asbestos causes the great majority of cases. **Q18.** A textile mill worker gets chest tightness that is worst on the first day back at work each week. The diagnosis is - (a) silicosis - (b) byssinosis (cotton, flax, hemp dust) - (c) farmer's lung - (d) asbestosis **Answer: (b)** — Endotoxin is the likely agent. **Q19.** Chronic beryllium disease is easily confused with - (a) sarcoidosis (both form granulomas) - (b) asbestosis - (c) TB always - (d) asthma **Answer: (a)** — Granulomas in lungs and intrathoracic nodes. **Q20.** The proportion of lung cancers related to cigarette smoking is about - (a) 25% - (b) 100% - (c) 50% - (d) 85% **Answer: (d)** — 15–20% occur in never or minimal smokers. **Q21.** A non-smoking woman develops lung cancer. The most likely histological type is - (a) large cell carcinoma - (b) adenocarcinoma - (c) squamous cell carcinoma - (d) small cell carcinoma **Answer: (b)** — The commonest subtype overall, especially in never-smokers. **Q22.** A smoker has shoulder and arm pain, hand wasting, ptosis and a small pupil on the same side. The lesion is - (a) a Pancoast (superior sulcus) tumour with Horner syndrome - (b) a central squamous carcinoma - (c) mesothelioma - (d) a cervical rib only **Answer: (a)** — Sympathetic chain involvement causes Horner syndrome. **Q23.** After a smoker quits, the risk of lung cancer - (a) returns to normal within a year - (b) falls but never returns to that of a never-smoker - (c) is unchanged - (d) rises **Answer: (b)** — MSD. **Q24.** A non-occupational radioactive gas that raises lung cancer risk, especially in smokers, is - (a) radon - (b) nitrogen - (c) ozone - (d) carbon monoxide **Answer: (a)** — Second leading cause of lung cancer in the US. **Q25.** The mutation found in about 91% of lung squamous cell carcinomas is in - (a) EGFR - (b) ALK - (c) KRAS - (d) TP53 **Answer: (d)** — Receptor tyrosine kinase mutations are less frequent in SCC. **Q26.** Lung cancer is first divided histologically into - (a) primary and secondary only - (b) small cell and non-small cell - (c) benign and malignant only - (d) central and peripheral only **Answer: (b)** — NSCLC includes adenocarcinoma, squamous and large cell. **Q27.** Which of these is a confirmed lung carcinogen besides tobacco smoke? - (a) fluoride - (b) caffeine - (c) vitamin C - (d) asbestos **Answer: (d)** — Also arsenic, chromium, nickel, coke-oven emissions. **Q28.** The disease that is the leading cause of cancer death in men and women worldwide is - (a) lung carcinoma - (b) breast cancer - (c) colon cancer - (d) prostate cancer **Answer: (a)** — MSD. **Q29.** Coal worker pneumoconiosis at its most severe becomes - (a) pleural plaques - (b) bronchiectasis - (c) progressive massive fibrosis - (d) mesothelioma **Answer: (c)** — COPD and bronchitis are common in miners. **Q30.** Asthma pathophysiology includes all of the following EXCEPT - (a) airway hyperreactivity - (b) airway remodelling - (c) bronchoconstriction - (d) alveolar wall destruction as the main lesion **Answer: (d)** — Alveolar wall destruction is emphysema. ### Active Recall From memory: name the commonest pneumonia pathogen and the atypicals; describe lung abscess cause and site; define chronic bronchitis and the role of alpha-1 antitrypsin; describe asthma and bronchiectasis; match silica, coal, asbestos, cotton and beryllium to their diseases; and summarise lung cancer risk factors, types, Pancoast tumour and mesothelioma.