Infectious Diseases — MCQs
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A 10-year-old boy presents with an ulcerated lesion with undermined edges over the upper chest, accompanied by a satellite lesion in the anterior axillary fold for two months. Axillary lymph nodes are palpable. Histopathology reveals a dermal abscess with ill-defined histiocytes. AFB staining of the tissue is positive. Chest X-ray shows infiltrations and cavities. Mantoux test is positive. What is the most likely diagnosis?
Earliest and often the only presentation of TB kidney is
Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?
Most common presentation of extra- pulmonary TB
The most common cause of seizures in a patient of AIDS is
Which of the following statements about herpes zoster complications is incorrect?
Which type of pulmonary TB is most likely to give sputum positive ?
A 17 years old female presents with sore throat and lymphadenopathy. A diagnostic test reveals the presence of heterophile antibodies. Diagnosis is?
What is a rare condition associated with Hepatitis B infection?
What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 1161: A 10-year-old boy presents with an ulcerated lesion with undermined edges over the upper chest, accompanied by a satellite lesion in the anterior axillary fold for two months. Axillary lymph nodes are palpable. Histopathology reveals a dermal abscess with ill-defined histiocytes. AFB staining of the tissue is positive. Chest X-ray shows infiltrations and cavities. Mantoux test is positive. What is the most likely diagnosis?
- A. Scrofuloderma (Correct Answer)
- B. Skin abscess
- C. Furuncle
- D. Cellulitis
- E. Erysipelas
Explanation: ### Scrofuloderma - The combination of an **ulcerated lesion with undermined edges**, **satellite lesions**, palpable **axillary lymph nodes** [1], positive **AFB staining** in tissue (indicating mycobacteria), and **pulmonary infiltrations/cavities** on chest X-ray are classic signs of scrofuloderma, a contiguous spread of tuberculosis from underlying structures to the skin. - A **positive Mantoux test** further supports a diagnosis of tuberculosis [1], and the histopathology showing a **dermal abscess with ill-defined histiocytes** is consistent with a tuberculous granulomatous reaction. ### Skin abscess - A skin abscess would typically present as a localized collection of **pus** and inflammation but would not usually have undermined edges, satellite lesions, or systemic involvement like pulmonary infiltrates or positive AFB staining for mycobacteria. - While histopathology might show an abscess, the presence of **ill-defined histiocytes** along with systemic signs points away from a simple bacterial abscess. ### Furuncle - A furuncle (boil) is a **deep folliculitis**, an infection of the hair follicle, usually caused by *Staphylococcus aureus*, presenting as a painful, red, pus-filled lump [2]. - It does not typically present with **undermined edges**, satellite lesions, or systemic findings such as pulmonary involvement or positive AFB staining for mycobacteria. ### Erysipelas - Erysipelas is a superficial skin infection, typically caused by **Group A Streptococcus**, characterized by a rapidly spreading, bright red, well-demarcated, and painful rash with a raised border. - It does not involve deep ulceration with undermined edges, satellite lesions, or the systemic pulmonary findings and positive AFB staining seen in this case. ### Cellulitis - Cellulitis is a bacterial infection of the subcutaneous tissue, manifesting as a poorly demarcated, red, swollen, and tender area that is usually not raised. - Unlike scrofuloderma, it does not typically present with **undermined ulcers**, satellite lesions, regional lymphadenopathy specifically related to tuberculosis, or the systemic and histopathological findings of mycobacterial infection.
Question 1162: Earliest and often the only presentation of TB kidney is
- A. Blood in urine (Correct Answer)
- B. Sterile pyuria
- C. Colicky abdominal pain
- D. Kidney stones
Explanation: ***Blood in urine*** - **Hematuria** (blood in urine) is a common initial presentation of renal TB, often microscopic and sometimes macroscopic, appearing early due to inflammation and ulceration of the urinary tract. - The presence of **blood in urine** without significant pain or other classic infection signs can confuse the diagnosis, making it an "early" and *misleading* symptom without further investigation. *Sterile pyuria* - While **sterile pyuria** (pus cells in urine without bacterial growth on routine cultures) is highly suggestive of **TB kidney**, it tends to appear later in the disease progression as more significant renal damage and inflammation occur. - Early stages might not show prominent pyuria, and **hematuria** often precedes it as the initial symptom of tissue damage. *Colicky abdominal pain* - **Colicky abdominal pain** is more commonly associated with obstruction, such as from stone passage or severe hydronephrosis, which are typically later complications of TB kidney, not early presentations. - Early renal TB typically involves the parenchyma and calyces, not usually leading to significant obstruction that would cause colicky pain. *Kidney stones* - **Kidney stones** (renal calculi) are a potential long-term complication of renal TB due to metabolic changes, inflammation, and cellular debris, but they are not an *early* or *initial* symptom [1]. - The formation of stones usually indicates more advanced disease or chronic inflammation within the urinary tract [1].
Question 1163: Tropical pulmonary eosinophilia is specifically associated with which of the following conditions?
- A. Occult filariasis (Correct Answer)
- B. Asthmatic bronchitis
- C. Pneumonic plague
- D. Cerebral malaria
Explanation: ***Occult filariasis*** - **Tropical pulmonary eosinophilia (TPE)** is a hypersensitivity reaction specifically caused by infection with **filarial parasites**, primarily *Wuchereria bancrofti* or *Brugia malayi*, in individuals living in endemic areas [1]. - The disease involves migration of microfilariae to the lungs, stimulating a strong **IgE-mediated immune response** leading to high eosinophil counts in the blood and lung tissue [1]. *Cerebral malaria* - **Cerebral malaria** is caused by the parasite *Plasmodium falciparum* and is characterized by neurological complications, not pulmonary eosinophilia. - It involves sequestration of parasitized red blood cells in the brain's microvasculature, leading to coma and other neurological symptoms. *Pneumonic plague* - **Pneumonic plague** is a severe bacterial infection caused by *Yersinia pestis*, affecting the lungs and leading to pneumonia. - It is not associated with eosinophilia and requires antibiotic treatment. *Asthmatic bronchitis* - **Asthmatic bronchitis** is a general term referring to inflammation of the bronchi combined with features of asthma, often triggered by allergens, irritants, or infections. - While it can involve eosinophilic inflammation, it is a broader syndrome and not specifically linked to occult filariasis in the way TPE is.
Question 1164: Most common presentation of extra- pulmonary TB
- A. Tubercular lymphadenitis (Correct Answer)
- B. Peritoneal TB
- C. Pericardial TB
- D. Tubercular meningitis
Explanation: ***Tubercular lymphadenitis*** - This is the **most common form** of extrapulmonary tuberculosis, often presenting as painless, swollen lymph nodes, especially in the cervical region [1]. - It develops when *Mycobacterium tuberculosis* disseminates from a primary pulmonary focus to regional lymph nodes, leading to granulomatous inflammation [1], [3]. *Peritoneal TB* - While a significant form of extrapulmonary TB, it is **less common** than lymphadenitis, typically presenting with abdominal pain, distension, and ascites. - Involvement of the peritoneum usually indicates hematogenous spread or direct extension from adjacent organs. *Pericardial TB* - This is a **rare but serious** form of extrapulmonary TB, often leading to pericardial effusion, constriction, or tamponade [2]. - It results from retrograde lymphatic spread or direct extension from mediastinal lymph nodes and is not the most common presentation. *Tubercular meningitis* - A **severe and life-threatening** form of extrapulmonary TB, involving the meninges of the brain and spinal cord, but it is less frequent than lymphadenitis [2]. - It is often seen in immunocompromised individuals or young children and presents with neurological symptoms [4].
Question 1165: The most common cause of seizures in a patient of AIDS is
- A. Toxoplasmosis (Correct Answer)
- B. Cryptococcal meningitis
- C. Progressive multifocal leucoencephalopathy
- D. CNS lymphoma
Explanation: ***Toxoplasmosis*** - **Cerebral toxoplasmosis** is the most common cause of focal neurological deficits and seizures in patients with AIDS [1]. - It typically presents with multiple **ring-enhancing lesions** on MRI, often in the basal ganglia [1]. *Cryptococcal meningitis* - While common in AIDS, **cryptococcal meningitis** primarily causes headache, fever, and altered mental status, but seizures are less frequent. - It is diagnosed by identifying **Cryptococcus neoformans** in CSF. *Progressive multifocal leucoencephalopathy* - PML is a demyelinating disease caused by the **JC virus** and results in progressive neurological deficits due to white matter lesions [2]. - Seizures can occur, but this condition primarily affects **cognition** and motor function [2]. *CNS lymphoma* - **Primary CNS lymphoma** is another common CNS complication in AIDS, often presenting as a solitary or multiple ring-enhancing lesion [1]. - While it can cause seizures, it is less common than toxoplasmosis as the primary cause of seizures in this population [1].
Question 1166: Which of the following statements about herpes zoster complications is incorrect?
- A. Chickenpox and herpes zoster are caused by the same virus (VZV)
- B. Herpes zoster typically occurs in a dermatomal distribution
- C. Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely
- D. Postherpetic neuralgia is the most common complication of herpes zoster (Correct Answer)
Explanation: ***Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely*** - While the **chickenpox vaccine** (varicella vaccine) is highly effective at preventing primary varicella (chickenpox) and significantly reduces the risk of herpes zoster (shingles), it does not offer **complete prevention** against either [1]. - Vaccinated individuals can still get a milder form of chickenpox, and they can still develop shingles, albeit at a reduced rate and often with less severe symptoms and a **lower risk of postherpetic neuralgia**. *Chickenpox and herpes zoster are caused by the same virus (VZV)* - This statement is correct; both conditions are caused by the **Varicella-Zoster Virus (VZV)**, a human herpesvirus [1]. - VZV causes primary infection (chickenpox) and then establishes latency in **sensory ganglia**, reactivating later as herpes zoster [1]. *Herpes zoster typically occurs in a dermatomal distribution* - This statement is correct; herpes zoster rash characteristically presents as a **unilateral vesicular eruption** confined to one or more contiguous **dermatomes** [1]. - This distribution reflects the reactivation of the virus from a single or adjacent **sensory ganglion** [1]. *Postherpetic neuralgia is the most common complication of herpes zoster* - This statement is correct; **postherpetic neuralgia (PHN)** is defined as pain that persists for at least 90 days after the onset of the zoster rash. - It is the **most frequent and debilitating long-term complication** of herpes zoster, particularly in older adults [1].
Question 1167: Which type of pulmonary TB is most likely to give sputum positive ?
- A. Fibronodular
- B. Pleural effusion
- C. Cavitary (Correct Answer)
- D. None of the options
Explanation: ***Cavitary*** - **Cavitary lesions** in pulmonary tuberculosis indicate extensive tissue destruction and high bacterial load, leading to a much higher likelihood of finding **acid-fast bacilli** in the sputum [1]. - The communication of these cavities with the airways allows for the expulsion of bacilli-laden material, making sputum microscopy a sensitive diagnostic tool [1]. *Fibronodular* - While fibronodular lesions indicate pulmonary TB, they typically represent areas of **healing or chronic, lower-grade infection** where the bacterial load may be lower. - Sputum positivity is possible but less frequent compared to cavitary disease, as the organisms are more contained within **granulomas** [2]. *Pleural effusion* - **Pleural effusions** in TB are often a result of a hypersensitivity reaction to mycobacterial antigens rather than direct mycobacterial invasion of the pleural space with high bacterial load. - Sputum smears are typically **negative** in cases of isolated tuberculous pleural effusion because the infection is primarily contained within the pleural space, not actively expelled from the lungs. *None of the options* - This option is incorrect because **cavitary pulmonary TB** is well-established as the form most frequently associated with sputum positivity [1]. - The presence of open cavities directly correlates with the ability to detect bacteria in expectorated samples.
Question 1168: A 17 years old female presents with sore throat and lymphadenopathy. A diagnostic test reveals the presence of heterophile antibodies. Diagnosis is?
- A. Tuberculosis (TB)
- B. Infectious mononucleosis (IM) (Correct Answer)
- C. Cytomegalovirus infection
- D. Streptococcal throat infection
Explanation: ***Infectious mononucleosis (IM)*** - The presence of **heterophile antibodies** in a patient with **sore throat** and **lymphadenopathy** is the diagnostic hallmark of infectious mononucleosis, commonly caused by the **Epstein-Barr virus (EBV)** [1]. - This clinical presentation, especially in a young adult, is highly suggestive of IM [1]. *Tuberculosis (TB)* - While TB can cause **lymphadenopathy** (e.g., scrofula), it typically presents with other systemic symptoms like **fever**, **night sweats**, and **weight loss**, and its diagnosis relies on microbial cultures, PCR, or biopsy, not heterophile antibodies [2]. - A sore throat is not a characteristic primary symptom of TB lymphadenitis. *Cytomegalovirus infection* - **Cytomegalovirus (CMV)** can cause a mononucleosis-like syndrome with symptoms similar to EBV, including fever, fatigue, and lymphadenopathy [3]. - However, CMV infection does **not typically produce heterophile antibodies**, which differentiates it from IM [3]. *Streptococcal throat infection* - **Streptococcal pharyngitis** causes a sore throat and can lead to cervical lymphadenopathy but is diagnosed by **rapid strep test** or **throat culture**. - It does **not involve heterophile antibody production** and typically lacks the widespread lymphadenopathy and fatigue seen in IM.
Question 1169: What is a rare condition associated with Hepatitis B infection?
- A. Wegener's granulomatosis
- B. Systemic lupus erythmatosus
- C. Polyarteritis nodosa (Correct Answer)
- D. Sjogren syndrome
Explanation: ***Polyarteritis nodosa*** - **Polyarteritis nodosa (PAN)** is a **necrotizing vasculitis** [1] strongly associated with **Hepatitis B virus (HBV)** infection, particularly in areas where HBV is endemic. - The circulating **immune complexes** formed by HBV antigens and antibodies are deposited in the walls of small and medium-sized arteries, leading to inflammation and tissue damage. *Wegener's granulomatosis* - Now known as **Granulomatosis with Polyangiitis (GPA)**, this condition is primarily associated with **antineutrophil cytoplasmic antibodies (ANCAs)**, particularly **c-ANCA**, and is not typically linked to Hepatitis B infection. - It is characterized by necrotizing granulomatous inflammation and vasculitis affecting the respiratory tract and kidneys. *Systemic lupus erythematosus* - **Systemic lupus erythematosus (SLE)** is an **autoimmune disease** characterized by widespread inflammation and damage to various organ systems, often involving **antinuclear antibodies (ANAs)** [2], [3]. - While it can be triggered by various factors, a direct and strong association with Hepatitis B infection is not a known characteristic. *Sjogren syndrome* - **Sjogren syndrome** is a chronic autoimmune disorder primarily affecting the **exocrine glands**, leading to **dry eyes** and **dry mouth**, and is associated with **anti-Ro/SSA** and **anti-La/SSB antibodies** [2]. - While autoimmune conditions can rarely coexist or be triggered by viral infections, a direct or common association between Sjogren syndrome and Hepatitis B infection is not established.
Question 1170: What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?
- A. HBsAg only
- B. HBsAg and HBV DNA
- C. HBsAg, HBeAg, and HBV DNA (Correct Answer)
- D. Anti-HBsAg and HBV DNA
Explanation: **HBsAg, HBeAg, and HBV DNA** - The presence of **HBsAg** indicates ongoing HBV infection [1], while **HBeAg** signifies active viral replication and high infectivity [1]. - **HBV DNA levels** directly quantify the amount of viral genetic material, providing a direct measure of viral load and disease activity [1]. *HBsAg only* - While **HBsAg** indicates the presence of HBV infection, it doesn't provide a complete picture of viral replication or load [1]. - It doesn't differentiate between active replication and chronic carriage with low viral activity [1]. *HBsAg and HBV DNA* - This combination is better than HBsAg alone, as **HBV DNA** directly measures viral load [1]. - However, it misses **HBeAg**, which is a crucial marker for active viral replication and high infectivity, especially in the early phases of chronic infection [2]. *Anti-HBsAg and HBV DNA* - **Anti-HBsAg** (HBsAb) indicates immunity to HBV, either from vaccination or resolved infection, and its presence suggests the absence of active infection [1]. - Therefore, the co-existence of **Anti-HBsAg** with significant **HBV DNA** levels is contradictory and unlikely to represent a high level of active HBV infection.
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