Internal Medicine
2 questionsPseudomembranous colitis, all are true except:
Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
NEET-PG 2013 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 701: Pseudomembranous colitis, all are true except:
- A. Blood in stools is a common feature (Correct Answer)
- B. Toxin A is responsible for clinical manifestation
- C. Summit lesions are early histopathological findings
- D. Toxin B is responsible for clinical manifestation
Explanation: ***Blood in stools is a common feature*** - While diarrhea is a hallmark of **pseudomembranous colitis**, **bloody stools** are uncommon and, if present, suggest severe disease or an alternative diagnosis [1]. - The typical presentation involves **watery diarrhea**, abdominal cramps, and fever, not usually overt bleeding [1]. *Toxin A is responsible for clinical manifestation* - **Toxin A (TcdA)** is one of the primary exotoxins produced by *Clostridioides difficile* and contributes significantly to the **inflammation** and fluid secretion seen in pseudomembranous colitis. - It acts as an **enterotoxin**, causing fluid secretion and mucosal damage in the colon [1]. *Summit lesions are early histopathological findings* - **Summit lesions**, also known as "summit pseudomembranes" or **"volcano lesions"**, refer to characteristic histological findings where inflammatory exudates effuse from the tips of damaged crypts. - These are typical early findings in pseudomembranous colitis, demonstrating the focal nature of the **mucosal injury**. *Toxin B is responsible for clinical manifestation* - **Toxin B (TcdB)** is another key exotoxin produced by *Clostridioides difficile*, and it is considered even more **cytotoxic** than Toxin A [1]. - It causes significant **cell damage** and **apoptosis**, playing a crucial role in the development of the pseudomembranes and clinical symptoms [1].
Question 702: Which of the following conditions is least commonly associated with Pneumocystis carinii in AIDS?
- A. Meningitis
- B. Otic polypoid mass (Correct Answer)
- C. Pneumonia
- D. Ophthalmic choroid lesion
Explanation: ***Otic polypoid mass*** - While *Pneumocystis jirovecii* (formerly *carinii*) can cause **extrapulmonary disease** in immunocompromised patients, an **otic polypoid mass** is an extremely rare and atypical presentation. - Extrapulmonary manifestations usually involve organs with rich vascular supply, but ear involvement in this form is not a characteristic feature. *Pneumonia* - **Pneumocystis pneumonia (PCP)** is the **most common opportunistic infection** and AIDS-defining illness caused by *Pneumocystis jirovecii* in individuals with AIDS [1]. - It typically manifests as **fever, cough, and dyspnea** with characteristic imaging findings [1]. *Ophthalmic choroid lesion* - **Choroid lesions** due to *Pneumocystis jirovecii* are a recognized, albeit less common, **extrapulmonary manifestation** in immunocompromised patients, particularly those with AIDS. - These lesions are usually **asymptomatic** and discovered incidentally on funduscopic examination. *Meningitis* - Although *Pneumocystis jirovecii* causing **meningitis** is rare, it has been reported in severely immunocompromised individuals with AIDS, often as part of disseminated disease. - Central nervous system involvement signifies **widespread dissemination** and advanced immunosuppression.
Microbiology
6 questionsWhich gene of Hepatitis B virus (HBV) is most commonly associated with mutations causing antiviral drug resistance?
Which of the following statements about malaria transmission is correct?
Amoebic liver abscess can be diagnosed by demonstrating-
Who discovered the bacterium Treponema pallidum?
Who discovered the bacterium Mycobacterium tuberculosis, which causes tuberculosis?
Which of the following bacteria does not exhibit bipolar staining?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 701: Which gene of Hepatitis B virus (HBV) is most commonly associated with mutations causing antiviral drug resistance?
- A. X gene
- B. S gene
- C. C gene
- D. P gene (Correct Answer)
Explanation: ***P gene*** - The **P gene** (polymerase gene) of HBV encodes the viral reverse transcriptase which is essential for viral replication. - Mutations in the P gene can lead to **antiviral drug resistance**, particularly to nucleos(t)ide analogues. *X gene* - The **X gene** encodes the X protein (HBx), a **transcriptional transactivator** involved in viral replication and pathogenesis. - While important for viral function, it is not the primary target for antiviral therapy, and mutations are less frequently associated with drug resistance. *S gene* - The **S gene** encodes the **surface antigens (HBsAg)**, which are crucial for viral entry and immune evasion. - Mutations in the S gene can lead to **vaccine escape mutants** or alter HBsAg detection, but not directly responsible for antiviral resistance. *C gene* - The **C gene** encodes the **core protein (HBcAg)** and the precore protein (HBeAg). - These proteins are involved in **viral particle assembly** and immune modulation, but mutations in this gene are not typically associated with resistance to antiviral drugs.
Question 702: Which of the following statements about malaria transmission is correct?
- A. Individuals harboring gametocytes can transmit malaria. (Correct Answer)
- B. P. vivax always completely fills the infected RBC with schizonts.
- C. Malaria can only be transmitted through blood transfusions.
- D. All stages of P. falciparum are commonly seen in peripheral blood smears.
Explanation: ***Individuals harboring gametocytes can transmit malaria.*** - **Gametocytes** are the sexual stage of the malaria parasite that circulate in the human bloodstream and are infectious to mosquitos. - When an *Anopheles* mosquito feeds on an infected human, it ingests these gametocytes, allowing the parasite's life cycle to continue in the mosquito vector, leading to transmission. *P. vivax always completely fills the infected RBC with schizonts.* - While *P. vivax* does infect **reticulocytes** (young RBCs) and can enlarge them, the **schizonts** typically occupy a significant portion but not always completely fill the host cell. - The infected RBCs are often enlarged to about 1.5 to 2 times their normal size and contain numerous **Schüffner's dots**. *Malaria can only be transmitted through blood transfusions.* - The primary mode of malaria transmission is through the bite of an **infected female *Anopheles* mosquito**. - While **blood transfusions** can transmit malaria, it is a less common and secondary route compared to vector-borne transmission. *All stages of P. falciparum are commonly seen in peripheral blood smears.* - In *P. falciparum* infections, only the **ring forms** and **gametocytes** are commonly observed in the peripheral blood smear. - The more mature asexual stages (trophozoites and schizonts) typically sequester in the capillaries of internal organs, where they are not readily visible in peripheral circulation.
Question 703: Amoebic liver abscess can be diagnosed by demonstrating-
- A. Trophozoites in the pus (Correct Answer)
- B. Trophozoites in the feces
- C. Cysts in the pus
- D. Cysts in the liver
Explanation: ***Trophozoites in the pus*** - **Amoebic liver abscesses** are caused by the invasive **trophozoite stage** of *Entamoeba histolytica*. - Demonstrating **trophozoites** in the characteristic **'anchovy paste' pus** aspirated from the abscess cavity is diagnostic. *Cysts in the pus* - **Cysts** are the **infective stage** of *Entamoeba histolytica* and are typically found in the **feces**, not in an abscess. - Cysts are responsible for transmission and survival outside the host, but they do not cause invasive disease. *Cysts in the liver* - The disease in the liver is caused by **trophozoites**, which invade the intestinal wall and then spread to the liver. - **Cysts** are never found within the liver parenchyma or abscesses. *Trophozoites in the feces* - While **trophozoites** can be found in the feces during acute amoebic dysentery, their presence alone does not confirm a liver abscess. - Furthermore, **trophozoites** are fragile and often difficult to detect in stool samples, especially once the stool has cooled.
Question 704: Who discovered the bacterium Treponema pallidum?
- A. Robert Koch
- B. Twort
- C. Ellerman
- D. Fritz Schaudinn and Erich Hoffmann (Correct Answer)
Explanation: ***Fritz Schaudinn and Erich Hoffmann*** - **Fritz Schaudinn** was a German zoologist, and **Erich Hoffmann** was a German dermatologist; they jointly discovered **Treponema pallidum** in **1905**. - Their discovery of the spirochete was a crucial step in understanding the etiology of **syphilis**. *Robert Koch* - **Robert Koch** is renowned for identifying the causative agents of **tuberculosis**, **cholera**, and **anthrax**. - He developed Koch's postulates, a fundamental set of criteria for establishing the causal relationship between a microbe and a disease. *Twort* - **Frederick Twort** was a British bacteriologist who is credited with the discovery of **bacteriophages** in **1915**. - His work involved examining transparent areas in bacterial cultures, leading to the identification of lytic viruses that infect bacteria. *Ellerman* - **Vilhelm Ellerman** was a Danish pathologist known for his work in **hematology** and **virology**. - Alongside **Olaf Bang**, he demonstrated that avian leukemia (erythroleukemia) could be transmitted by a filterable agent, indicating a viral etiology for some cancers.
Question 705: Who discovered the bacterium Mycobacterium tuberculosis, which causes tuberculosis?
- A. Jenner
- B. Louis Pasteur
- C. Robert Koch (Correct Answer)
- D. Lister
Explanation: ***Robert Koch*** - **Robert Koch** discovered the bacterium *Mycobacterium tuberculosis* in **1882**, identifying its role as the causative agent of tuberculosis. - His work was crucial in establishing the germ theory of disease and earned him the Nobel Prize in Physiology or Medicine in 1905. *Louis Pasteur* - **Louis Pasteur** was a pioneer in microbiology, known for his work on **pasteurization**, **vaccinations** (e.g., rabies and anthrax), and disproving spontaneous generation. - While he made significant contributions to understanding infectious diseases, he did not discover *Mycobacterium tuberculosis*. *Lister* - **Joseph Lister** was a British surgeon who revolutionized surgery by introducing **antiseptic techniques** using carbolic acid to prevent infections. - His contributions were fundamental to reducing mortality rates from surgical infections, but he did not discover the tuberculosis bacterium. *Jenner* - **Edward Jenner** is famous for developing the **smallpox vaccine**, which was a groundbreaking achievement in immunology and public health. - His work, though vital for preventing infectious diseases, predates and is unrelated to the discovery of *Mycobacterium tuberculosis*.
Question 706: Which of the following bacteria does not exhibit bipolar staining?
- A. Haemophilus influenzae (Correct Answer)
- B. Yersinia pestis
- C. Calymmatobacterium granulomatis
- D. Francisella tularensis
Explanation: ***Haemophilus influenzae*** - *Haemophilus influenzae* is a **pleomorphic coccobacillus** that typically stains uniformly and does not exhibit characteristic **bipolar staining**. - Its presence is often identified by Gram stain showing small, Gram-negative rods, but without the distinctive safety pin appearance. *Calymmatobacterium granulomatis* - *Calymmatobacterium granulomatis* (now *Klebsiella granulomatis*) is known to exhibit **bipolar staining**, often described as a **"safety pin" appearance**, especially in tissue smears from granuloma inguinale lesions. - This characteristic staining is due to the concentration of stain at the ends of the rod-shaped bacteria. *Yersinia pestis* - *Yersinia pestis*, the causative agent of plague, is classically described as having **bipolar staining**, giving it a distinctive **"safety pin" appearance** under a microscope. - This finding is a key diagnostic feature, particularly when observed in Gram-stained smears of clinical samples. *Francisella tularensis* - *Francisella tularensis* is a small, Gram-negative coccobacillus that is known to exhibit **bipolar staining**, though it may be less prominent than in *Yersinia pestis*. - This characteristic can assist in the microscopic identification of the bacterium, which causes tularemia.
Pathology
1 questionsThe most common subtype of Non-Hodgkin's lymphoma in India is:
NEET-PG 2013 - Pathology NEET-PG Practice Questions and MCQs
Question 701: The most common subtype of Non-Hodgkin's lymphoma in India is:
- A. Diffuse small cell lymphocytic lymphoma
- B. Diffuse large B cell lymphoma (Correct Answer)
- C. Follicular lymphoma
- D. Burkitt's lymphoma
Explanation: ***Diffuse large B cell lymphoma*** - It is the most common subtype of **Non-Hodgkin's lymphoma** observed in India, reflecting a higher prevalence in the population. - Characterized by **aggressive clinical behavior** [1] and typically presents as a rapidly enlarging mass, often involving lymph nodes or extranodal sites. *Burkitt's lymphoma* - This subtype is known for its **high proliferation rate** and is more common in specific demographics, such as children and immunocompromised individuals. - It typically presents with **jaw lesions** or abdominal masses, which is not typical in the broader Indian population. *Diffuse small cell lymphocytic lymphoma* - More accurately classified as **chronic lymphocytic leukemia** (CLL), it is not the most common subtype of Non-Hodgkin's lymphoma. - Characterized by a **milder clinical course** and presents with lymphocytosis in peripheral blood, lacking aggressive features. *Follicular lymphoma* - This is usually a **low-grade lymphoma** associated with **indolent behavior** and may not be the most commonly diagnosed subtype in India. - It typically involves multiple lymph nodes and is characterized by **nodular patterns on histology**, making it less prevalent than diffuse large B cell lymphoma. Follicular lymphoma is rare in Asian populations [2]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 563-564. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 602-604.
Pharmacology
1 questionsWhich of the following is the longest acting glucocorticoid?
NEET-PG 2013 - Pharmacology NEET-PG Practice Questions and MCQs
Question 701: Which of the following is the longest acting glucocorticoid?
- A. Prednisone
- B. Prednisolone
- C. Cortisone
- D. Dexamethasone (Correct Answer)
Explanation: ***Correct: Dexamethasone*** - **Dexamethasone** is a long-acting glucocorticoid with a **biological half-life of 36–72 hours**, making it the longest acting among the options provided - Its prolonged action is due to its **high affinity for the glucocorticoid receptor** and relatively slow metabolism - Provides sustained anti-inflammatory and immunosuppressive effects *Incorrect: Prednisone* - **Prednisone** is an intermediate-acting glucocorticoid with a biological half-life of 12-36 hours - Requires metabolism in the liver to its active form, prednisolone - Duration of action is significantly shorter than dexamethasone *Incorrect: Prednisolone* - **Prednisolone** is the active form of prednisone, with a similar intermediate duration of action (12-36 hours) - Primarily used when liver conversion of prednisone is impaired - Does not possess the extended duration of action characteristic of dexamethasone *Incorrect: Cortisone* - **Cortisone** is a short-acting glucocorticoid with a biological half-life of 8-12 hours - It is a prodrug that needs to be converted to **hydrocortisone** (cortisol) in the liver to become active - Has the shortest duration among all options