Pulmonary Infections — MCQs
Air bronchogram on chest X-ray denotes -
Which of the following features is NOT typically seen in viral pneumonia?
A 6-year-old boy presents with fever and chills, cough, rapid breathing, difficulty breathing, and chest pain. A culture from a respiratory sample shows Gram-positive bacteria. What is the most likely organism causing this infection?
In primary tuberculosis, what is seen?
A 50-year-old male with hemoptysis shows cavitary lesion with air-crescent sign. Most likely diagnosis?
Which condition is characterized by a specific appearance on CT scans that resembles small centrilobular nodules with branching linear structures?
A 65-year-old male presents with fever, chills, and a productive cough with rust-colored sputum. What is the most likely diagnosis?
Which of the following conditions characteristically causes bilateral hypertranslucency of lung fields on chest X-ray?
Identify the most likely diagnosis based on the chest X-ray findings in a patient with low-grade fever.
On CT chest, the 'halo sign' is particularly associated with which condition in immunocompromised patients?
Pulmonary Infections Indian Medical PG Practice Questions and MCQs
Question 1: Air bronchogram on chest X-ray denotes -
- A. Intrapulmonary lesion (Correct Answer)
- B. Extrapulmonary lesion
- C. Intrathoracic lesion
- D. Extrathoracic lesion
Explanation: ***Intrapulmonary lesion*** - An **air bronchogram** indicates that the air-filled bronchi are surrounded by consolidated or fluid-filled alveoli, making the bronchi visible against the opacified lung parenchyma. - This pattern is a strong sign of a process **within the lung tissue itself**, such as pneumonia, pulmonary edema, or malignancy. *Extrapulmonary lesion* - **Extrapulmonary lesions**, such as pleural effusions or masses originating from the chest wall, typically displace or compress the lung and bronchi, rather than filling the alveoli around them. - They usually do **not produce an air bronchogram** because the air in the bronchi is not juxtaposed against diseased lung parenchyma. *Intrathoracic lesion* - This is a broad term that includes all lesions within the thoracic cavity, both intrapulmonary and extrapulmonary. - While an air bronchogram is an intrathoracic finding, it specifically points to an **intrapulmonary process**, not just any intrathoracic lesion. *Extrathoracic lesion* - **Extrathoracic lesions** are located outside the chest cavity and would not manifest as an air bronchogram on a chest X-ray. - This option is **completely unrelated** to the interpretation of an air bronchogram.
Question 2: Which of the following features is NOT typically seen in viral pneumonia?
- A. Bronchiolitis
- B. Multinucleate giant cells in the bronchiolar wall
- C. Predominance of alveolar exudate (Correct Answer)
- D. Presence of interstitial inflammation
Explanation: ### Predominance of alveolar exudate - Viral pneumonia typically involves the **interstitium**, leading to interstitial inflammation, rather than a significant accumulation of **exudate** within the alveoli [3]. - **Alveolar exudate** is more characteristic of **bacterial pneumonia**, where neutrophils and fibrin fill the alveolar spaces [1], [2], [3]. ### Presence of interstitial inflammation - This is a **hallmark pathological feature** of viral pneumonia, where inflammatory cells infiltrate the alveolar septa and peribronchial tissues [3]. - The inflammation primarily involves the **walls of the alveoli** and the **surrounding connective tissue**, not the alveolar lumen. ### Bronchiolitis - Viral infections, especially in children, often affect the **small airways (bronchioles)**, causing inflammation and obstruction. - This can lead to symptoms such as **wheezing** and **dyspnea** in viral pneumonia. ### Multinucleate giant cells in the bronchiolar wall - The presence of **multinucleate giant cells** is a specific histological finding associated with certain viral pneumonias, particularly those caused by **measles** and **respiratory syncytial virus (RSV)**. - These cells arise from the fusion of infected cells and are found within the bronchiolar epithelium and lumen. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 317-318. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 711-712. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 715.
Question 3: A 6-year-old boy presents with fever and chills, cough, rapid breathing, difficulty breathing, and chest pain. A culture from a respiratory sample shows Gram-positive bacteria. What is the most likely organism causing this infection?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae (Correct Answer)
- C. Staphylococcus aureus
- D. Propionibacterium acnes
Explanation: ***Streptococcus pneumoniae*** - This clinical picture describes typical symptoms of **pneumonia** in a child, including fever, cough, rapid and difficult breathing, and chest pain. - **_Streptococcus pneumoniae_** is the most common bacterial cause of community-acquired pneumonia in children. The respiratory sample showing gram-positive bacteria further supports this. *Staphylococcus aureus* - While **_Staphylococcus aureus_** can cause pneumonia, it is less common than _Streptococcus pneumoniae_ in community-acquired cases in healthy children and often associated with more severe, necrotizing forms or post-viral infections. - While it is a **Gram-positive bacterium**, its clinical presentation would not be the most likely first choice for typical pneumonia symptoms in this age group. *Propionibacterium acnes* - **_Propionibacterium acnes_** (now *Cutibacterium acnes*) is primarily associated with **acne vulgaris** and, less commonly, opportunistic infections related to implanted devices or some rare soft tissue infections. - It is not a typical cause of primary respiratory infections like pneumonia. *Streptococcus pyogenes* - **_Streptococcus pyogenes_** (Group A Streptococcus) is known for causing **pharyngitis** (strep throat), skin infections (impetigo, cellulitis), and scarlet fever. - While it can rarely cause pneumonia, it is not a common cause, and the constellation of symptoms points more strongly to _Streptococcus pneumoniae_.
Question 4: In primary tuberculosis, what is seen?
- A. Ghon's focus (Correct Answer)
- B. Pleural effusion
- C. Miliary mottling
- D. Fibrosis
Explanation: ***Ghon's focus*** - A **Ghon's focus** is the primary parenchymal lesion that develops at the site of initial infection in **primary tuberculosis**. - It consists of a small area of caseous necrosis in the lung parenchyma, typically in the **mid or lower zones**. - Combined with hilar lymph node involvement, it forms the **Ghon complex (primary complex)**, which is the pathological hallmark of primary TB. - This represents the **characteristic pathological finding** that defines primary tuberculosis [2]. *Pleural effusion* - **Pleural effusion** is actually a **common manifestation of primary tuberculosis**, particularly in adolescents and adults [3]. - It develops due to a hypersensitivity reaction to tubercular antigens in the pleural space. - While frequently seen in primary TB, it is a **clinical manifestation** rather than the defining pathological lesion (Ghon's focus). - Can occur in both primary and post-primary TB [3]. *Miliary mottling* - **Miliary mottling** on chest X-ray is characteristic of **miliary tuberculosis**, a severe form where the infection disseminates hematogenously [1]. - This represents a **complication of primary TB** due to lymphohematogenous spread, not the typical presentation [1]. - Shows multiple small nodules (1-3mm) scattered throughout both lung fields. *Fibrosis* - **Fibrosis** refers to scarring of lung tissue that occurs during the **healing phase** of tuberculosis. - It is a **sequela of TB infection**, not an acute finding in primary tuberculosis. - Develops after the active infection has been controlled or treated [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 320-321. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 379-380. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 728-729.
Question 5: A 50-year-old male with hemoptysis shows cavitary lesion with air-crescent sign. Most likely diagnosis?
- A. Tuberculosis
- B. Aspergilloma (Correct Answer)
- C. Granulomatosis with polyangiitis (GPA)
- D. Lung abscess
Explanation: ***Aspergilloma*** - The presence of a **cavitary lesion** with an **air-crescent sign** (Monod sign) in a patient with hemoptysis is highly characteristic of an aspergilloma, which is a fungal ball growing within a pre-existing lung cavity. - **Hemoptysis** is a common symptom due to the erosion of vessels by the fungal ball or inflammation. *Tuberculosis* - While **cavitary lesions** can be seen in tuberculosis, the **air-crescent sign** is not typical and hemoptysis in TB is usually related to active infection or rupture of an aneurysm (Rasmussen's aneurysm). - Tuberculosis would typically show other features like **consolidation**, **lymphadenopathy**, or **miliary opacities** depending on the stage. *Granulomatosis with polyangiitis (GPA)* - GPA can cause **cavitary lung lesions** and **hemoptysis** due to parenchymal vasculitis. - However, it does not typically present with the definitive **air-crescent sign** seen with aspergilloma. GPA would also show signs of **renal involvement** and **upper airway disease**. *Lung abscess* - A lung abscess is a **pus-filled cavity** in the lung often caused by bacterial infection, appearing as a cavitary lesion in imaging. - While it can cause hemoptysis, the **air-crescent sign** is not a characteristic feature; instead, it typically shows a **thick, irregular wall** with an air-fluid level.
Question 6: Which condition is characterized by a specific appearance on CT scans that resembles small centrilobular nodules with branching linear structures?
- A. Pulmonary tuberculosis (Correct Answer)
- B. Silicosis
- C. Pulmonary hydatid cyst
- D. Small cell carcinoma
Explanation: ***Pulmonary tuberculosis*** - This description ("small centrilobular nodules with **branching linear structures**") is characteristic of the **tree-in-bud pattern** seen on CT scans, which is a hallmark finding in active **endobronchial spread of tuberculosis**. - The tree-in-bud pattern results from the impaction of tuberculous **granulomas** and caseous material in the terminal and respiratory bronchioles. *Silicosis* - Characterized by multiple small, well-defined **nodules** (often in the upper lobes) that tend to calcify, but typically lacks the fine **branching linear structures**. - It’s associated with occupational exposure to **silica dust** and may progress to **massive progressive fibrosis**. *Pulmonary hydatid cyst* - Presents as a well-defined, usually **single, large cystic lesion** on CT, often with internal membranes if ruptured (water lily sign or crumpled membrane sign). - It does not typically manifest with small centrilobular nodules or branching linear structures. *Small cell carcinoma* - Usually appears as a **large central mass**, often with mediastinal lymphadenopathy, and sometimes associated with obstructive pneumonitis. - It does not typically present as diffuse small centrilobular nodules with branching patterns.
Question 7: A 65-year-old male presents with fever, chills, and a productive cough with rust-colored sputum. What is the most likely diagnosis?
- A. TB
- B. Klebsiella pneumonia
- C. Pneumocystis pneumonia
- D. Pneumococcal Pneumonia (Correct Answer)
Explanation: Pneumococcal Pneumonia - This presentation with fever, chills, and rust-colored sputum is classic for pneumococcal pneumonia, caused by Streptococcus pneumoniae [1]. [2] - The rust color results from the presence of hemolyzed red blood cells from the inflamed alveoli [3]. TB - While TB can cause fever and cough, the sputum is typically mucoid or purulent, and sometimes hemoptysis (frank blood) is seen, but not usually rust-colored [4]. - TB symptoms tend to be more chronic, including night sweats and weight loss, which are not mentioned here. Klebsiella pneumonia - Klebsiella pneumoniae typically causes severe pneumonia, often in individuals with alcoholism or diabetes [1]. - It classically presents with currant jelly sputum, which is distinct from rust-colored sputum [2]. Pneumocystis pneumonia - Pneumocystis jirovecii pneumonia (PCP) primarily affects immunocompromised individuals, particularly those with HIV [4]. - Symptoms are usually more insidious, involving dyspnea, non-productive cough, and hypoxia, and sputum is not typically rust-colored [4].
Question 8: Which of the following conditions characteristically causes bilateral hypertranslucency of lung fields on chest X-ray?
- A. Mcleod syndrome
- B. Poland syndrome
- C. Emphysema (Correct Answer)
- D. Pneumothorax
Explanation: ***Correct: Emphysema*** - **Emphysema** causes destruction of alveolar walls, leading to enlarged air spaces and **air trapping**, making both lungs appear hypertranslucent on X-ray - This **bilateral hypertranslucency** is due to reduced lung tissue density, decreased vascular markings, and increased air volume - Classic radiographic features include flattened diaphragms, increased retrosternal space, and hyperlucent lung fields *Incorrect: Mcleod syndrome* - Also known as **Swyer–James–MacLeod syndrome**, this condition causes **unilateral** lung or lobe hyperlucency due to post-infectious obliterative bronchiolitis - The key differentiating feature is that it's **unilateral**, whereas the question asks for bilateral hypertranslucency - Affected lung shows air trapping on expiratory films *Incorrect: Pneumothorax* - A **pneumothorax** presents as a **unilateral** or focal hypertranslucent area due to air in the pleural space - Characterized by **absence of lung markings** beyond the visceral pleural line and associated lung collapse - This is a pleural space abnormality, not a bilateral parenchymal lung disease *Incorrect: Poland syndrome* - **Poland syndrome** is a congenital condition with absence or underdevelopment of the pectoralis major muscle - Can lead to **unilateral** apparent hyperlucency on the affected side due to missing chest wall muscle - This is a **chest wall anomaly**, not a parenchymal lung disease causing bilateral hypertranslucency
Question 9: Identify the most likely diagnosis based on the chest X-ray findings in a patient with low-grade fever.
- A. ILD
- B. Bronchopneumonia
- C. Miliary TB (Correct Answer)
- D. Consolidation
Explanation: ***Miliary TB*** - The chest X-ray shows diffuse, small, uniformly distributed nodular opacities (2-3 mm in diameter) bilaterally, characteristic of "**millet seed**" pattern seen in **miliary tuberculosis**. - This pattern results from the hematogenous spread of *Mycobacterium tuberculosis* throughout the lungs, often presenting with **low-grade fever** and constitutional symptoms. *ILD* - **Interstitial lung disease (ILD)** typically shows reticular, nodular, or ground-glass opacities, sometimes with honeycombing, but the pattern is usually more heterogeneous and often basal or peripheral, unlike the uniform fine nodularity seen here. - While some ILDs can present with diffuse nodular patterns, the clinical context of **fever** and the classic "millet seed" appearance are more indicative of miliary TB. *Bronchopneumonia* - **Bronchopneumonia** presents as patchy, often ill-defined, multifocal areas of opacification or consolidation, usually distributed around the bronchi. - It does not typically cause the fine, diffuse, and uniform nodular pattern seen in this image, which represents widespread interstitial or alveolar involvement rather than primarily bronchial inflammation. *Consolidation* - **Consolidation** appears as a homogeneous opacification that obliterates vessels and airway walls, often with air bronchograms, typically confined to a lobe or segment. - The image shows diffuse nodular infiltrates rather than large, confluent areas of homogeneous opacification, making isolated consolidation an unlikely primary description.
Question 10: On CT chest, the 'halo sign' is particularly associated with which condition in immunocompromised patients?
- A. Pulmonary hydatid cyst
- B. Round pneumonia
- C. Bronchiectasis
- D. Invasive pulmonary aspergillosis (Correct Answer)
Explanation: ***Invasive pulmonary aspergillosis*** - The **halo sign** on CT chest, characterized by a ground-glass opacity surrounding a nodule, is a classic radiographic finding in **invasive pulmonary aspergillosis**, especially in immunocompromised patients. - This sign represents hemorrhage around the fungal nodule and indicates active tissue invasion by *Aspergillus* species. *Pulmonary hydatid cyst* - Hydatid cysts are typically well-defined, thin-walled cystic lesions, often displaying the **water lily sign** if complicated by rupture, which is different from the halo sign. - These cysts are caused by the larval stage of *Echinococcus granulosus* and are not associated with a peripheral ground-glass opacity. *Round pneumonia* - Round pneumonia is a localized, **spherical consolidation** often seen in children, which does not typically exhibit the perilesional ground-glass opacity characteristic of the halo sign. - It usually represents bacterial infection and resolves with antibiotics, unlike the invasive fungal disease suggested by the halo sign. *Bronchiectasis* - Bronchiectasis is characterized by **irreversible dilation of the bronchi**, often appearing as "tram-track" opacities or "signet ring" signs on CT. - It is a chronic condition related to airway damage and mucus retention, and not associated with acute nodular lesions or the halo sign.
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