Respiratory Pathology — MCQs

Respiratory Pathology Indian Medical PG Practice Questions and MCQs

Question 161: Which type of shock is characterized by the development of 'shock lung'?

A. Hypovolemic shock
B. Septic shock (Correct Answer)
C. Anaphylactic shock
D. Neurogenic shock

Explanation: **Explanation:** **Shock lung** is the historical clinical term for **Acute Respiratory Distress Syndrome (ARDS)** [1]. It is characterized by diffuse alveolar damage (DAD), leading to severe hypoxemia and pulmonary edema [1]. **Why Septic Shock is the correct answer:** Septic shock is the most common cause of ARDS. In sepsis, systemic inflammation triggers the release of potent cytokines (TNF, IL-1) [2]. These cytokines activate neutrophils, which lodge in pulmonary capillaries and release reactive oxygen species (ROS) and proteases [2]. This causes extensive damage to the alveolar-capillary membrane, leading to protein-rich fluid leakage into the alveoli and the formation of characteristic **hyaline membranes** [1]. **Analysis of Incorrect Options:** * **Hypovolemic Shock:** While severe trauma can lead to ARDS, pure volume loss (hemorrhage) typically affects the kidneys (Acute Tubular Necrosis) before the lungs. * **Anaphylactic Shock:** This is a Type I hypersensitivity reaction characterized by bronchospasm and laryngeal edema rather than diffuse alveolar damage. * **Neurogenic Shock:** This results from a loss of sympathetic tone leading to peripheral vasodilation; it does not typically manifest with the inflammatory lung injury seen in "shock lung." **High-Yield Clinical Pearls for NEET-PG:** * **Pathological Hallmark:** The presence of **Hyaline Membranes** lining the alveolar walls [1]. * **Key Cells:** Neutrophils are the primary mediators of injury in ARDS [2]. * **Exudative Phase:** Occurs in the first 0–7 days (edema and hyaline membranes) [1]. * **Proliferative Phase:** Occurs after 1 week (type II pneumocyte proliferation and fibrosis) [1]. * **Radiology:** Characterized by bilateral "white-out" on chest X-ray with a normal capillary wedge pressure (<18 mmHg) [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 679-681. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 142-143.

Question 162: Which of the following does not cause cavitation in the lung parenchyma?

A. Squamous cell carcinoma
B. Tuberculosis
C. Hamartoma (Correct Answer)
D. Staphylococcus pneumonia

Explanation: **Explanation:** Lung cavitation occurs when central necrosis within a lesion communicates with a bronchus, allowing the necrotic material to be expelled and replaced by air. **Why Hamartoma is the correct answer:** A **Hamartoma** is the most common benign tumor of the lung [1]. It is a slow-growing, well-circumscribed mass composed of tissues normally found in the lung (cartilage, fat, and connective tissue) but in a disorganized mass. Because it lacks a rapid growth rate and does not undergo central ischemic necrosis or liquefaction, it **does not cavitate**. On imaging, it classically presents as a "coin lesion" with characteristic **"popcorn calcification."** **Analysis of Incorrect Options:** * **Squamous Cell Carcinoma (SCC):** Among bronchogenic carcinomas, SCC is the most likely to cavitate (approx. 10-15% of cases) [2]. This is due to rapid growth leading to central obstructive ischemia and subsequent necrosis [3]. * **Tuberculosis (TB):** Cavitation is a hallmark of **Secondary (Reactivation) TB**. It results from a robust cell-mediated immune response leading to caseous necrosis, which liquefies and drains into the bronchial tree. * **Staphylococcus pneumonia:** *S. aureus* is a pyogenic bacterium that produces potent toxins and enzymes, leading to tissue destruction and abscess formation [4]. These abscesses frequently result in thin-walled air-filled cavities known as **pneumatoceles**, especially in children. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Cavitary Lung Lesions (CAVITY):** **C**ancer (SCC), **A**utoimmune (Wegener’s), **V**ascular (Infarct), **I**nfection (TB, Fungal, Abscess), **T**rauma, **Y**outh (CPAM). * **Most common cancer to cavitate:** Squamous Cell Carcinoma [2]. * **Most common cause of fungal cavitation:** Aspergilloma (Monod sign/Air-crescent sign). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 727-728. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 336-337. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 723-724. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 715-716.

Question 163: Bronchocentric granulomatosis commonly occurs due to?

A. Hypersensitivity reaction to Aspergillus (Correct Answer)
B. Immunological reaction to HIV
C. Damage by c-ANCA
D. Damage by p-ANCA

Explanation: **Explanation:** **Bronchocentric Granulomatosis (BG)** is a unique histopathological pattern characterized by necrotizing granulomatous inflammation centered primarily on the walls of small bronchi and bronchioles. 1. **Why Option A is Correct:** In the majority of cases (especially in asthmatic patients), BG is considered a severe **hypersensitivity reaction to *Aspergillus fumigatus*** [1]. It is often viewed as a pathological manifestation of **Allergic Bronchopulmonary Aspergillosis (ABPA)** [2]. The fungal hyphae trigger an intense immune response, leading to "mucoid impaction" and the replacement of bronchial epithelium with palisading granulomas and eosinophilic debris. 2. **Why the Other Options are Incorrect:** * **Option B (HIV):** While HIV patients are prone to opportunistic infections (like TB or PCP) that cause granulomas, BG is not a recognized primary immunological manifestation of HIV. * **Option C & D (ANCA):** c-ANCA is the hallmark of **Granulomatosis with Polyangiitis (GPA)**, and p-ANCA is associated with **Eosinophilic Granulomatosis with Polyangiitis (EGPA/Churg-Strauss)** [3]. While these are granulomatous vasculitides, BG is specifically "bronchocentric" rather than "angiocentric" (vessel-centered). In BG, any vascular involvement is secondary to the nearby bronchial inflammation. **NEET-PG High-Yield Pearls:** * **Histology:** Look for "Palisading granulomas" surrounding necrotic centers containing eosinophils (Eosinophilic pneumonia). * **Stains:** Silver stains (GMS/PAS) may show occasional non-invasive fungal hyphae within the mucus. * **Clinical Association:** Strongly associated with **Asthma** and **Peripheral Eosinophilia**. * **Differential:** Unlike GPA (Wegener’s), BG typically lacks systemic vasculitis and is ANCA-negative. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 690-691. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 396-397. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 322-323.

Question 164: What is the characteristic histopathological feature of Pneumocystis carinii pneumonia?

A. Interstitial pneumonitis
B. Increased eosinophils
C. Foamy vacuolated exudates
D. Mononuclear cells in bronchoalveolar lavage (Correct Answer)

Explanation: **Explanation:** **Pneumocystis jirovecii (formerly P. carinii)** is an opportunistic fungal pathogen primarily affecting immunocompromised patients, particularly those with HIV/AIDS (CD4 count <200 cells/µL) [1]. **Why Option D is Correct:** The diagnosis of Pneumocystis pneumonia (PCP) is typically confirmed through **Bronchoalveolar Lavage (BAL)** or induced sputum. Histologically, the alveolar spaces are filled with a characteristic **"cotton-candy" or foamy eosinophilic exudate** [1]. Within this exudate, a cellular response is observed. While the exudate itself is acellular, the host immune response—even if blunted—results in an influx of **mononuclear cells** (macrophages and lymphocytes) into the alveolar spaces and interstitium. BAL fluid analysis characteristically shows these mononuclear cells alongside the trophic forms and cysts of the organism. **Analysis of Incorrect Options:** * **Option A (Interstitial pneumonitis):** While PCP causes thickening of the alveolar septa, the hallmark is the *intra-alveolar* exudate rather than a primary interstitial process like viral pneumonia [1]. * **Option B (Increased eosinophils):** Eosinophilia is not a feature of PCP; it is more characteristic of allergic bronchopulmonary aspergillosis (ABPA) or Löffler syndrome. * **Option C (Foamy vacuolated exudates):** While "foamy exudate" is a classic description, the question asks for a specific *histopathological feature* often identified in diagnostic samples like BAL. In many competitive exams, the presence of mononuclear cells in the lavage is considered the definitive cellular finding. **High-Yield Clinical Pearls for NEET-PG:** * **Stain of Choice:** **Gomori Methenamine Silver (GMS)** stain highlights the "crushed ping-pong ball" or "cup-and-saucer" shaped cysts [1]. * **Radiology:** Classic "ground-glass opacities" (GGO) radiating from the hilum. * **Treatment:** Trimethoprim-sulfamethoxazole (TMP-SMX) is the first-line drug for both prophylaxis and treatment. * **Biomarker:** Elevated serum **Beta-D-Glucan** is a sensitive but non-specific marker for PCP. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 318-319.

Question 165: In hyaline membrane disease, what is the primary pathological component in the lung?

A. Albumin and complement
B. Fibrin (Correct Answer)
C. Precipitated surfactant
D. Mucus

Explanation: **Explanation:** Hyaline Membrane Disease (HMD), also known as Infant Respiratory Distress Syndrome (IRDS), is primarily caused by a deficiency of **surfactant** [2]. This deficiency leads to high alveolar surface tension, resulting in widespread atelectasis and alveolar injury. **Why Fibrin is correct:** The core pathology involves damage to the alveolar epithelial cells (Type I pneumocytes) and capillary endothelial cells due to hypoxia. This injury leads to increased capillary permeability, causing a protein-rich fluid to leak into the alveolar spaces [1]. This exudate, rich in **fibrin** and cellular debris, coagulates to form the characteristic "glassy" eosinophilic (pink) membranes that line the alveoli [1]. **Analysis of Incorrect Options:** * **A. Albumin and complement:** While albumin is present in the exudate, fibrin is the structural hallmark that forms the distinct membrane. Complement is not a primary component of these membranes. * **C. Precipitated surfactant:** HMD is defined by a *lack* of surfactant (specifically dipalmitoylphosphatidylcholine). The membranes are a result of the injury caused by this absence, not the surfactant itself [2]. * **D. Mucus:** Mucus is produced by goblet cells and bronchial glands; it is not a constituent of the hyaline membranes found in the distal airspaces. **High-Yield Clinical Pearls for NEET-PG:** * **Microscopy:** Eosinophilic, amorphous membranes lining the respiratory bronchioles and alveolar ducts [1]. * **Risk Factors:** Prematurity (most common), Maternal Diabetes (insulin inhibits surfactant synthesis), and Cesarean section (lack of "vaginal squeeze" stress which triggers surfactant release) [2]. * **L/S Ratio:** A Lecithin/Sphingomyelin ratio of **<2:1** in amniotic fluid indicates fetal lung immaturity. * **Treatment:** Antenatal corticosteroids (e.g., Betamethasone) to the mother and postnatal exogenous surfactant to the neonate. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 679-681. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 465-467.

Question 166: Which of the following is a tumor marker for lung cancer?

A. S-100
B. CEA (Correct Answer)
C. CD-99
D. Beta 2 microglobulin

Explanation: **Explanation:** **Carcinoembryonic Antigen (CEA)** is the correct answer. It is a glycoprotein primarily associated with colorectal carcinoma but is also a well-recognized tumor marker for **Adenocarcinoma of the lung**. While not specific enough for initial diagnosis, CEA levels are clinically significant for monitoring treatment response, detecting recurrence, and predicting prognosis in non-small cell lung cancer (NSCLC) [1]. **Analysis of Incorrect Options:** * **S-100:** This is a marker for cells derived from the neural crest. It is highly sensitive for **Melanoma**, Schwannomas, and Langerhans Cell Histiocytosis (LCH). * **CD-99 (MIC2):** This is a highly specific cell surface marker for **Ewing’s Sarcoma** and Primitive Neuroectodermal Tumors (PNET). * **Beta 2 microglobulin:** This marker is primarily used in hematological malignancies, most notably **Multiple Myeloma** and certain lymphomas, to determine tumor burden and prognosis. **High-Yield Clinical Pearls for NEET-PG:** * **Adenocarcinoma** is now the most common histological subtype of lung cancer in both smokers and non-smokers. * **IHC Markers for Lung Cancer:** * **Adenocarcinoma:** TTF-1 (Thyroid Transcription Factor-1) and Napsin A. * **Squamous Cell Carcinoma:** p40, p63, and Cytokeratin 5/6. * **Small Cell Carcinoma:** Chromogranin A, Synaptophysin, and CD56 (Neural Cell Adhesion Molecule). * CEA is also elevated in heavy smokers without malignancy, which must be considered during clinical correlation [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, p. 346.

Question 167: Pneumatocele is most commonly caused by which organism?

A. Staphylococcus (Correct Answer)
B. Streptococcus
C. Streptococcus pneumoniae
D. P. carnii

Explanation: **Explanation:** **Pneumatocele** is a thin-walled, air-filled cyst within the lung parenchyma. It most commonly occurs as a complication of acute bacterial pneumonia, specifically when caused by **Staphylococcus aureus** [1]. **Why Staphylococcus is correct:** *Staphylococcus aureus* produces specific toxins and enzymes (such as Panton-Valentine Leukocidin) that cause focal **necrosis** of the bronchial wall and adjacent alveoli. This creates a "check-valve" mechanism where air enters the interstitial space during inspiration but becomes trapped during expiration. This localized obstructive emphysema leads to the characteristic thin-walled, air-filled tension cysts seen on chest X-rays. **Analysis of Incorrect Options:** * **Streptococcus (Group A):** While it can cause necrotizing pneumonia and empyema, it rarely leads to the specific valvular air-trapping required for pneumatocele formation. * **Streptococcus pneumoniae:** This is the most common cause of community-acquired pneumonia (CAP) [1]. It typically causes lobar consolidation and is less likely to cause significant tissue necrosis or cavitation compared to *S. aureus* [1]. * **P. jirovecii (formerly P. carinii):** While it can cause "pneumatoceles" or subpleural blebs in HIV/immunocompromised patients (leading to pneumothorax), *Staphylococcus* remains the most common cause in the general and pediatric populations, making it the standard answer for this classic board question. **High-Yield Pearls for NEET-PG:** 1. **Pediatric Association:** Pneumatoceles are most frequently seen in children following Staphylococcal pneumonia. 2. **Management:** Most pneumatoceles are asymptomatic and resolve spontaneously; surgical intervention is rarely required unless they cause tension pneumothorax. 3. **Other Staphylococcal Complications:** Always look for **Empyema** and **Pyopneumothorax** as co-existing findings with *S. aureus* infections. 4. **Radiology:** They appear as smooth, thin-walled cavities that can change size rapidly on serial X-rays. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 709-715.

Question 168: Reactivated tuberculosis is most commonly located near which anatomical region?

A. Apex (Correct Answer)
B. Bronchus
C. Subpleural region
D. Base

Explanation: **Explanation:** **Correct Option: A (Apex)** Reactivated (Secondary) Tuberculosis typically localizes to the **apex of the upper lobes** (or the superior segments of the lower lobes) [1]. This predilection is due to the high **Ventilation-Perfusion (V/Q) ratio** found in the apices. *Mycobacterium tuberculosis* is an obligate aerobe; the higher alveolar oxygen tension ($P_AO_2$) in the apex provides an ideal environment for the bacilli to flourish after reactivation of a latent focus. **Analysis of Incorrect Options:** * **B. Bronchus:** While TB can spread via the endobronchial route (causing endobronchial TB), it is a complication or a mode of spread rather than the primary site of reactivation [1]. * **C. Subpleural region:** This is the characteristic location of the **Ghon focus** in **Primary Tuberculosis**, typically found in the lower part of the upper lobe or upper part of the lower lobe [1]. * **D. Base:** The bases have a lower V/Q ratio and lower oxygen tension compared to the apices, making them less favorable for the growth of reactivation TB. **NEET-PG High-Yield Pearls:** * **Ghon Complex:** Consists of a parenchymal subpleural lesion (Ghon focus) + draining lymphadenopathy [1]. * **Ranke Complex:** A radiologically visible healed Ghon complex that has undergone calcification. * **Assmann Focus:** The specific infraclavicular lesion seen in secondary TB. * **Simon’s Focus:** Apical nodules formed during hematogenous seeding in primary TB that later serve as the site for secondary reactivation. * **Morphology:** Secondary TB is characterized by **caseous necrosis** and **cavitation**, which is less common in primary TB (except in immunocompromised patients) [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 319-321.

Question 169: Asbestosis causes all of the following except?

A. Shaggy heart borders
B. Honeycombing
C. Hilar lymphadenopathy (Correct Answer)
D. Basal peribronchial fibrosis

Explanation: **Explanation:** Asbestosis is a form of diffuse interstitial pulmonary fibrosis caused by the inhalation of asbestos fibers [1]. The correct answer is **Hilar lymphadenopathy**, as this is characteristically **absent** in asbestosis. Its presence should prompt a clinician to consider alternative diagnoses such as Sarcoidosis, Silicosis, or malignancy. **Why Hilar Lymphadenopathy is the correct answer:** Unlike Silicosis (which causes "eggshell" calcification of hilar nodes) or Sarcoidosis, Asbestosis is primarily a fibrotic process of the lung parenchyma and pleura [1]. It does not typically involve the lymphatic system to an extent that causes gross adenopathy. **Analysis of incorrect options:** * **Shaggy heart borders:** This is a classic radiological sign of asbestosis. It occurs when extensive pleural thickening and parenchymal fibrosis blur the distinct interface between the heart and the lungs. * **Honeycombing:** This represents the end-stage of any progressive interstitial lung disease [2]. In asbestosis, advanced fibrosis leads to the formation of cystic spaces (honeycombing), typically in the lower lobes [1]. * **Basal peribronchial fibrosis:** Asbestos fibers are heavy and tend to settle in the lower lobes. Fibrosis typically begins in the peribronchiolar regions of the **lower lobes (basal)**, distinguishing it from Silicosis and Coal Worker’s Pneumoconiosis, which primarily affect the upper lobes [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Asbestos Bodies (Ferruginous bodies):** Golden-brown, fusiform/beaded rods with translucent centers, coated with iron-containing protein. * **Pleural Plaques:** The most common manifestation of asbestos exposure; usually involve the parietal pleura and the diaphragm [1]. * **Malignancy:** Asbestosis increases the risk of both Lung Carcinoma and Mesothelioma. **Lung Carcinoma** is the most common malignancy associated with asbestos, but **Mesothelioma** is the most specific. * **Rule of Thumb:** "Asbestos is from the bottom (Lower lobes), Silica is from the top (Upper lobes)." **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 698-699. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 691-692.

Question 170: Asbestosis of the lung is associated with all of the following EXCEPT?

A. Mesothelioma
B. Progression of lesion even after stopping exposure to asbestos
C. Nodular lesions involving upper lobe (Correct Answer)
D. Asbestos bodies in sputum

Explanation: **Explanation:** Asbestosis is a form of diffuse interstitial pulmonary fibrosis caused by the inhalation of asbestos fibers. The correct answer is **C** because asbestosis typically involves the **lower lobes** of the lungs, unlike most other pneumoconioses (like Silicosis or Coal Worker’s Pneumoconiosis) which primarily affect the upper lobes [1]. **Why Option C is the correct "EXCEPT" choice:** Asbestosis begins in the lower lobes and subpleural regions [1]. The lesions are characterized by **diffuse interstitial fibrosis**, not discrete nodular lesions. Nodular lesions are a hallmark of Silicosis, whereas Asbestosis presents with a "honeycomb" lung pattern in advanced stages. **Analysis of other options:** * **A. Mesothelioma:** Asbestos exposure is the only well-established environmental risk factor for malignant mesothelioma (pleural and peritoneal) [1]. * **B. Progression after stopping exposure:** Once the asbestos fibers are inhaled, they remain in the lung parenchyma. These fibers continue to trigger chronic inflammation and reactive oxygen species, leading to progressive fibrosis even after the source of exposure is removed. * **C. Asbestos bodies in sputum:** These are golden-brown, fusiform, or beaded rods with a translucent center (ferruginous bodies). Their presence in sputum or lung biopsy indicates significant asbestos exposure. **NEET-PG High-Yield Pearls:** * **Most common cancer in Asbestosis:** Bronchogenic carcinoma (not mesothelioma) [1]. * **Synergistic effect:** Smoking + Asbestos exposure increases the risk of bronchogenic carcinoma by ~55 times. * **Pleural Plaques:** These are the most common manifestation of asbestos exposure (usually on the parietal pleura and diaphragm) but do not contain asbestos bodies [1]. * **Prussian Blue Stain:** Used to identify asbestos bodies (stains the iron-containing protein coat). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 698-699.

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Congenital Anomalies

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Atelectasis and Acute Lung Injury

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Obstructive Pulmonary Diseases

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Restrictive Pulmonary Diseases

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Lung Infections

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Pulmonary Vascular Diseases

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Lung Tumors

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Pleural Diseases

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Interstitial Lung Diseases

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Occupational Lung Diseases

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