Anatomy
1 questionsB cells are located in which region of lymph nodes?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 191: B cells are located in which region of lymph nodes?
- A. Paracortical region
- B. Cortical follicles (Correct Answer)
- C. Subcapsular region
- D. Medullary sinuses
Explanation: ***Cortical follicles*** - **B cells** are predominantly found within the **cortical follicles** of lymph nodes, where they mature and become activated upon encountering antigens [2]. - These follicles can be primary (inactive) or secondary (active, containing **germinal centers** for B cell proliferation and differentiation). *Paracortical region* - The **paracortical region** is primarily occupied by **T cells** and is the site where T cells interact with antigen-presenting cells [1]. - While it's adjacent to B cell areas, it's not the primary location for B cells. *Medullary sinuses* - **Medullary sinuses** are channels in the medulla of the lymph node, containing macrophages and plasma cells, which are *differentiated B cells*. - They are not the primary residence for undifferentiated B cells. *Subcapsular region* - **Subcapsular region** is the space immediately beneath the capsule of the lymph node where lymph initially enters. - It contains macrophages and dendritic cells that sample antigens but is not a primary B cell zone.
Internal Medicine
1 questionsWhat is the mode of inheritance for the most common form of hypophosphatemic rickets?
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 191: What is the mode of inheritance for the most common form of hypophosphatemic rickets?
- A. Autosomal Recessive (AR)
- B. Autosomal Dominant (AD)
- C. X-Linked Recessive (XR)
- D. X-Linked Dominant (XD) (Correct Answer)
Explanation: ***X-Linked Dominant (XD)*** - The most common form of hypophosphatemic rickets is **X-linked hypophosphatemic rickets (XLH)**, which is inherited in an X-linked dominant pattern. - This condition is caused by mutations in the **PHEX gene** on the X chromosome, leading to impaired phosphate reabsorption in the kidneys. *Autosomal Recessive (AR)* - While some rare forms of hypophosphatemic rickets exist with **autosomal recessive** inheritance, they are not the most common. - These forms typically involve mutations in genes affecting phosphate transport or vitamin D metabolism, distinct from the primary defect in XLH. *Autosomal Dominant (AD)* - There are also rare **autosomal dominant** forms of hypophosphatemic rickets, such as hereditary hypophosphatemic rickets with hypercalciuria (HHRH) or autosomal dominant hypophosphatemic rickets (ADHR). - However, these are less common than the X-linked dominant form (XLH). *X-Linked Recessive (XR)* - **X-linked recessive** inheritance typically affects males more severely and exclusively, with carrier females usually unaffected or mildly affected. - In X-linked dominant conditions like XLH, both males and females are affected, though females may exhibit variable expressivity.
Pathology
6 questionsPost-streptococcal glomerulonephritis (PSGN) is an example of which type of hypersensitivity?
What is the number of antigens typically evaluated in comprehensive HLA matching for organ transplantation?
What is the most common type of graft rejection?
What is the initial event in serum sickness?
Which genetic condition is considered the most lethal due to monosomy?
Which of the following is a chromosomal instability syndrome?
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 191: Post-streptococcal glomerulonephritis (PSGN) is an example of which type of hypersensitivity?
- A. Type -1 hypersensitivity
- B. Type -2 hypersensitivity
- C. Type -3 hypersensitivity (Correct Answer)
- D. Type -4 hypersensitivity
Explanation: ***Type -3 hypersensitivity*** - Post-streptococcal glomerulonephritis (PSGN) is caused by **immune complex deposition**, a hallmark of type III hypersensitivity reactions [1][2][3]. - It involves the formation of **antigen-antibody complexes** following a streptococcal infection, leading to inflammation in the kidneys [1][2]. *Type -1 hypersensitivity* - Characterized by **IgE-mediated** reactions, such as allergies and anaphylaxis, which do not apply to PSGN. - It typically involves **mast cells** and histamine release, notably absent in PSGN cases. *Type -4 hypersensitivity* - Involves **T-cell mediated** responses and is related to delayed-type reactions, not applicable to PSGN. - Common examples include **contact dermatitis** and graft-versus-host disease, differing fundamentally from PSGN's mechanism. *Type -2 hypersensitivity* - Characterized by **antibody-mediated cytotoxicity**, such as in hemolytic anemia, unrelated to immune complexes in PSGN. - Typically involves direct damage to cells, contrasting with the immune complex mechanism observed in PSGN [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 214-215. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 910-915. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 215-216.
Question 192: What is the number of antigens typically evaluated in comprehensive HLA matching for organ transplantation?
- A. 10 (Correct Answer)
- B. 4
- C. 16
- D. 22
Explanation: ***10*** - The **number of criteria for HLA matching** in organ transplantation is typically 10, consisting of 6 class I and 4 class II antigens. - Proper HLA matching is critical for minimizing the risk of **graft rejection** and ensuring **recipient compatibility** [1]. *16* - While there are various HLA antigens, a total of **16** criteria is not a standard number used for matching purposes. - This number may include other factors but does not represent the core criteria for **HLA matching**. *4* - HLA matching involves more than **4 criteria**, inadequate for reliable transplantation outcomes. - This number does not encompass the essential **class I and class II antigens** that are necessary for effective matching. *22* - A total of **22 criteria** exceeds the conventional standard for HLA matching, which is not practical or necessary. - This figure may relate to overall HLA typing but is not applicable for the matching process itself. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 179-180.
Question 193: What is the most common type of graft rejection?
- A. Hyperacute
- B. Acute (Correct Answer)
- C. Chronic
- D. Acute on chronic
Explanation: ***Acute*** - **Acute rejection** is the most common type of graft rejection, occurring in **10-40% of transplant recipients**. [1] - It typically occurs **days to weeks to months** after transplantation (most commonly within the first 6 months). [1] - Mediated primarily by **T-lymphocytes** (cellular rejection) or **antibodies** (antibody-mediated rejection) reacting against donor antigens. [1] - Usually **responsive to immunosuppressive therapy** when detected early. *Hyperacute* - **Hyperacute rejection** is rare (occurs in <1% of cases) due to routine **pre-transplant cross-matching**. - Occurs within **minutes to hours** after transplantation due to **pre-existing circulating antibodies** against donor antigens. [1] - Results in immediate thrombosis and graft necrosis, requiring **immediate graft removal**. [1] *Chronic* - **Chronic rejection** (chronic allograft dysfunction) develops **months to years** after transplantation. - It is the **most common cause of late graft failure**, but not the most common type of rejection episode. - Characterized by **gradual, progressive loss of graft function** with vascular and fibrotic changes. - **Largely irreversible** and poorly responsive to treatment. *Acute on chronic* - This is **not a primary category** of graft rejection but represents an **acute rejection episode superimposed** on a graft already undergoing chronic changes. - Reflects exacerbation in a chronically rejecting graft. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 239-242.
Question 194: What is the initial event in serum sickness?
- A. It is associated with hypocomplementemia.
- B. It is a type III hypersensitivity reaction.
- C. It occurs due to exposure to heterologous antigens. (Correct Answer)
- D. It can lead to leukocytoclastic vasculitis.
Explanation: ***Can lead to leukocytoclastic vasculitis*** - Serum sickness is characterized by the formation of **immune complexes**, which can trigger **leukocytoclastic vasculitis** affecting the blood vessels [1][2]. - Symptoms can include **rash, fever, and arthralgia**, typically occurring 1-3 weeks after exposure to the offending antigen [2]. *Can occur due to homologous antigen* - Serum sickness is usually a reaction to **heterologous** antigens, such as those from animal serum, not **homologous** ones. - Homologous antigens do not typically elicit the immune response seen in serum sickness; hence, this statement is incorrect. *Type 2 hypersensitivity* - Serum sickness is classified as a **Type III hypersensitivity** reaction due to the immune complex formation, not Type II [1]. - Type II is characterized by antibody-mediated destruction of **target cells**, which does not apply here. *Hypercomplementemia* - Serum sickness is associated with **hypocomplementemia** due to complement consumption from immune complex formation, not hypercomplementemia. - This can lead to **decreased complement levels** during the response, making this statement incorrect. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 214-216. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 172-173.
Question 195: Which genetic condition is considered the most lethal due to monosomy?
- A. Autosomal monosomy (Correct Answer)
- B. Chromosomal monosomy
- C. Autosomal trisomy
- D. Chromosomal trisomy
Explanation: ***Autosomal monosomy*** - **Autosomal monosomy** is the most lethal form of monosomy because it involves the loss of an entire autosome, leading to a severe imbalance in gene dosage. [1] - The human body cannot typically survive with the loss of a whole autosome, resulting in early embryonic or fetal demise. [1] *Chromosomal monosomy* - This is a broader term that includes both **autosomal monosomy** and **sex chromosome monosomy**. - While many forms of chromosomal monosomy are lethal, **sex chromosome monosomy (e.g., Turner syndrome)** is survivable, making the general term "chromosomal monosomy" less specific for the *most lethal* condition. [1] *Autosomal trisomy* - **Autosomal trisomy** involves an extra copy of an autosome (e.g., Trisomy 21 for Down syndrome), which, while causing significant health issues, is generally less lethal than the complete loss of an autosome. [1] - Many individuals with autosomal trisomies can survive to birth and beyond, unlike most cases of autosomal monosomy. [1] *Chromosomal trisomy* - This refers to having an extra copy of any chromosome, including **autosomes** and **sex chromosomes**. - While conditions like **Trisomy 13 (Patau syndrome)** and **Trisomy 18 (Edwards syndrome)** are highly lethal, the presence of *extra* genetic material is typically less universally lethal than the *absence* of an entire autosome. [1] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 168-169.
Question 196: Which of the following is a chromosomal instability syndrome?
- A. Bloom syndrome (Correct Answer)
- B. Fanconi anemia
- C. Ataxia-telangiectasia
- D. None of the options
Explanation: ***Bloom syndrome*** - Bloom syndrome is the **classic chromosomal instability syndrome** characterized by **spontaneous chromosomal breaks, gaps, and markedly increased sister chromatid exchanges (SCEs)**. - It is an **autosomal recessive disorder** caused by mutations in the BLM gene (RecQ helicase family), leading to impaired DNA repair and replication [1]. - Patients exhibit **growth deficiency, photosensitive facial erythema, immunodeficiency**, and a dramatically **increased risk of cancers** at an early age. - The **hallmark laboratory finding** is a 10-fold increase in sister chromatid exchanges, making it the **prototypical chromosomal instability disorder**. *Fanconi anemia* - Fanconi anemia is **also a chromosomal instability syndrome**, characterized by **chromosomal breakage** when lymphocytes are exposed to DNA crosslinking agents (DEB/MMC test) [1]. - However, it presents primarily with **progressive bone marrow failure, congenital anomalies** (thumb/radial ray, café-au-lait spots, short stature), and increased cancer risk (particularly AML and squamous cell carcinomas). - While chromosomal instability is present, the **clinical presentation is dominated by bone marrow failure**, distinguishing it from Bloom syndrome. *Ataxia-telangiectasia* - Ataxia-telangiectasia is **also a chromosomal instability syndrome** with chromosomal breaks and translocations (especially involving chromosomes 7 and 14) [1]. - Caused by **ATM gene mutations**, leading to defective DNA double-strand break repair and cell cycle checkpoint control. - However, it is **clinically characterized primarily by progressive cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency**, and elevated AFP levels. - The **neurological manifestations predominate** the clinical picture, distinguishing it from Bloom syndrome. *None of the options* - This option is incorrect because Bloom syndrome is the **classic and prototypical chromosomal instability syndrome**, characterized predominantly by chromosomal instability features rather than other system involvement. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 322-323.
Psychiatry
1 questionsAll of the following are true about Down syndrome except for one.
NEET-PG 2015 - Psychiatry NEET-PG Practice Questions and MCQs
Question 191: All of the following are true about Down syndrome except for one.
- A. Incidence of Robertsonian translocation is 1:1000 (Correct Answer)
- B. Most common cause is trisomy 21
- C. Mosaicism 21 has no association with maternal age
- D. Extra chromosome is of maternal origin
- E. Incidence increases with advanced maternal age
Explanation: **Incidence of Robertsonian translocation is 1:1000** - This statement is **not accurate** for Down syndrome. Robertsonian translocation accounts for only about **3-4% of Down syndrome cases**, not a general population incidence of 1:1000. - The vast majority of Down syndrome cases (~95%) are due to trisomy 21 from nondisjunction, not translocation. - This is the **correct answer** as it is the FALSE statement. *Extra chromosome is of maternal origin* - In approximately **90-95% of Down syndrome cases**, the extra copy of chromosome 21 originates from the mother due to **nondisjunction** during meiosis. - This maternal origin is strongly correlated with **advanced maternal age**. *Most common cause is trisomy 21* - **Trisomy 21** (due to meiotic nondisjunction) accounts for about **95% of all Down syndrome cases**, making it the most common genetic mechanism. - This results in three separate copies of chromosome 21 in all body cells. *Mosaicism 21 has no association with maternal age* - **Mosaic Down syndrome** occurs when nondisjunction happens *after fertilization* in early embryonic development, leading to a mixture of cells with normal and trisomic cells. - Because it is a **post-zygotic event**, its incidence is independent of **maternal age**, unlike full trisomy 21. *Incidence increases with advanced maternal age* - **TRUE statement** - The risk of Down syndrome (particularly trisomy 21) increases significantly with **maternal age**. - Risk is approximately 1:1500 at age 20, 1:1000 at age 30, 1:400 at age 35, and 1:100 at age 40. - This is due to increased risk of meiotic nondisjunction in older oocytes.
Surgery
1 questionsWhich solid organ is considered to have the lowest risk of rejection during transplantation?
NEET-PG 2015 - Surgery NEET-PG Practice Questions and MCQs
Question 191: Which solid organ is considered to have the lowest risk of rejection during transplantation?
- A. Pancreas
- B. Kidney
- C. Heart
- D. Liver (Correct Answer)
Explanation: ***Liver*** - The liver has a unique immunologic environment, often referred to as **immunologic privilege**, which contributes to its lower rates of rejection compared to other transplanted solid organs. - It produces various **immunosuppressive factors** and has a high capacity for regeneration and repair, adapting more readily to the recipient's immune system. - The liver's **dual blood supply** (hepatic artery and portal vein) and tolerogenic properties make it the most immunologically privileged solid organ. *Pancreas* - **Pancreas transplantation** carries a high risk of rejection, with rejection rates significantly higher than liver transplantation. - Pancreatic tissue is highly **immunogenic** due to its endocrine and exocrine functions, requiring aggressive immunosuppression. - Often transplanted with kidney in diabetic patients, and rejection episodes are common. *Kidney* - Kidney transplantation is common, but it carries a significant risk of both **acute and chronic rejection**, requiring lifelong immunosuppression. - The kidney expresses various **MHC antigens** that are readily recognized by the recipient's immune system, making it more immunogenic than the liver. *Heart* - **Heart transplantation** is associated with a high risk of rejection due to the rich vascularity and immunogenicity of cardiac tissue. - It often requires aggressive immunosuppressive regimens to prevent both **acute cellular rejection** and **antibody-mediated rejection**.