FMGE 2024 — Pathology
4 Previous Year Questions with Answers & Explanations
Which blood is transfused in a patient with a Bombay blood group?
A 10-year-old boy is brought to the ED after being stung by a bee while playing outside. Within minutes of the sting, he developed shock, respiratory failure, and vascular collapse. What type of hypersensitivity reaction is most likely responsible?
Which of the following is the investigation of choice for CML?
A 5-year-old child presents with a lesion in the right eye. Histopathology reveals the presence of Flexner-Wintersteiner rosettes. What is the likely diagnosis?
FMGE 2024 - Pathology FMGE Practice Questions and MCQs
Question 1: Which blood is transfused in a patient with a Bombay blood group?
- A. A
- B. O negative (Correct Answer)
- C. AB
- D. B
Explanation: ⚠️ **IMPORTANT CLINICAL NOTE**: Patients with Bombay blood group (Oh phenotype) can **ONLY safely receive Bombay (Oh) blood** from another Bombay donor. **None of the standard ABO blood types listed below are correct or safe** for transfusion. ***Bombay Blood (Oh) - THE ONLY CORRECT ANSWER (Not Listed)*** - Bombay patients lack the **H antigen** due to deficiency of fucosyltransferase enzyme - They produce potent **anti-H, anti-A, and anti-B antibodies** [1] - **Only Bombay (Oh) blood is compatible** - this is the true correct answer - Standard blood banks must maintain rare Bombay donor registries for these patients **Why the listed options are ALL incorrect:** *O negative (Marked as "correct" but clinically WRONG)* - O negative blood **contains the H antigen**, which is present in all standard ABO groups [1] - Transfusing O negative to a Bombay patient causes **severe acute hemolytic transfusion reaction** due to anti-H antibodies - While O negative lacks A and B antigens, the presence of **H antigen makes it incompatible and dangerous** - This is a common misconception that must be avoided in clinical practice *A* - Contains **A antigen and H antigen** - Causes immediate hemolytic reaction from both **anti-A and anti-H antibodies** - Completely incompatible *B* - Contains **B antigen and H antigen** [1] - Causes rapid hemolysis from both **anti-B and anti-H antibodies** - Completely incompatible *AB* - Contains **A antigen, B antigen, and H antigen** - Causes massive hemolytic reaction from all three antibodies - Most incompatible of all standard blood types **Clinical Pearl**: Bombay phenotype is rare (~1 in 10,000 in India). Always maintain autologous blood storage or identify compatible Bombay donors in advance for these patients. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 627-628.
Question 2: A 10-year-old boy is brought to the ED after being stung by a bee while playing outside. Within minutes of the sting, he developed shock, respiratory failure, and vascular collapse. What type of hypersensitivity reaction is most likely responsible?
- A. A. IgE-mediated reaction (Correct Answer)
- B. D. T cell-mediated response
- C. B. IgG-mediated reaction
- D. C. IgA-mediated hypersensitivity
Explanation: A. IgE-mediated reaction - This is a **Type I hypersensitivity reaction** (anaphylaxis) [2], characterized by the rapid release of potent mediators (like **histamine** and leukotrienes) from mast cells and basophils upon re-exposure to an allergen (bee venom) [1][3][4]. - The clinical presentation of rapid onset **shock**, **respiratory failure**, and **vascular collapse** minutes after exposure is the classic, life-threatening manifestation of systemic anaphylaxis [5]. *B. IgG-mediated reaction* - IgG is the primary mediator in **Type II (cytotoxic)** and **Type III (immune complex)** hypersensitivity reactions, which are typically delayed (hours to days) and not immediate [2]. - Type II reactions involve antibody binding directly to cell surface antigens (e.g., hemolytic anemia), while Type III involves tissue damage from soluble immune complexes (e.g., serum sickness) [2]. *C. IgA-mediated hypersensitivity* - IgA is predominantly found in mucosal secretions and protects mucosal barriers; it is not the main antibody responsible for classic Type I systemic anaphylaxis. - While IgA can be implicated in various disorders (such as **celiac disease**), it does not mediate the massive, immediate systemic degranulation seen in bee sting-induced shock. *D. T cell-mediated response* - This refers to **Type IV hypersensitivity**, which is a **delayed reaction** mediated by sensitized T lymphocytes and macrophages (e.g., contact dermatitis, tuberculin test). - Type IV reactions typically take 24–72 hours to manifest and lack the rapid, humoral-driven vasodilation and bronchospasm characteristic of Type I anaphylaxis. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 688-689. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 210-211. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 211-212. [5] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 212-213.
Question 3: Which of the following is the investigation of choice for CML?
- A. LAP score
- B. FISH
- C. Molecular testing (BCR-ABL PCR)
- D. Karyotyping (Correct Answer)
Explanation: ***Karyotyping (Conventional Cytogenetics)*** - **Gold standard** and investigation of choice for CML diagnosis - Detects the **Philadelphia chromosome t(9;22)** present in 95% of CML cases [2] - WHO diagnostic criterion for CML - Can identify additional chromosomal abnormalities with prognostic significance - Provides complete chromosomal analysis *FISH (Fluorescence In Situ Hybridization)* - Used as **complementary technique** when karyotyping fails or metaphases are inadequate - More sensitive than karyotyping but NOT the first-line investigation [2] - Useful for monitoring minimal residual disease - Cannot detect additional chromosomal abnormalities *Molecular testing (BCR-ABL PCR)* - Used for **monitoring treatment response** and detecting minimal residual disease [1] - Highly sensitive and quantitative [1] - Not the initial investigation of choice for diagnosis *LAP score (Leukocyte Alkaline Phosphatase)* - Used to differentiate CML from leukemoid reaction - Low in CML, high in leukemoid reaction - Older diagnostic tool, now largely replaced by molecular methods - Not the investigation of choice **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Genetic Disorders, pp. 185-187. [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. 225-226.
Question 4: A 5-year-old child presents with a lesion in the right eye. Histopathology reveals the presence of Flexner-Wintersteiner rosettes. What is the likely diagnosis?
- A. Optic nerve glioma
- B. Rhabdomyosarcoma
- C. Retinoblastoma (Correct Answer)
- D. Ocular melanoma
Explanation: ***Retinoblastoma*** - The presence of **Flexner-Wintersteiner rosettes**, which are characteristic arrangements of columnar cells around a central lumen, is the pathognomonic histological feature of well-differentiated **retinoblastoma** [1].- This tumor is the most common **intraocular malignancy** of childhood, typically presenting as **leukocoria** (white pupillary reflex) in children under the age of 5. *Optic nerve glioma*- These tumors are typically low-grade astrocytomas, most frequently **pilocytic astrocytomas**, characterized by glial cells, not neuronal-like rosettes.- They involve the **optic nerve** itself and are strongly associated with **Neurofibromatosis type 1 (NF1)**. *Rhabdomyosarcoma*- This is the most common **pediatric orbital malignancy** (outside the globe), typically presenting with rapid onset of **proptosis** (exophthalmos) and eyelid swelling.- Histologically, it is a small round blue cell tumor derived from mesenchymal cells, showing **rhabdomyoblasts**, and does not form Flexner-Wintersteiner rosettes. *Ocular melanoma*- This malignancy is extremely rare in the pediatric population and is overwhelmingly a disease of **adults**.- Histopathology shows malignant cells derived from **melanocytes** (spindle or epithelioid cells) containing melanin, lacking photoreceptor differentiation structures like rosettes. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Eye, p. 1342.