FMGE 2024 - Pathology PYQs Practice Questions

Q: Which blood is transfused in a patient with a Bombay blood group?

O negative. ⚠️ **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. [Practice more Pathology PYQs on OnCourse]

Q: A 27-year-old pregnant female in her first trimester presents to the OPD for a regular antenatal checkup. During blood type screening, potential ABO incompatibility is discussed. The healthcare provider explains that certain antibody types are less concerning than others during pregnancy. ABO incompatibility does not occur due to which antibody in her case?

IgM. ***IgM***- The predominant natural antibodies against **ABO antigens** (anti-A and anti-B) are of the **IgM class**, which are large pentameric molecules. These **IgM antibodies** generally cannot cross the placenta due to their size, meaning they do not reach the fetal circulation and cause significant hemolytic disease of the newborn (HDN). *IgA*- IgA is predominantly found in secretions (mucous membranes, breast milk) and is not generally involved in causing **hemolytic disease of the newborn (HDN)**, as it does not cross the placenta in significant amounts. This antibody class is not the primary mechanism of incompatibility, as the most common non-transmissible antibodies are IgM. *IgG*- **IgG is the only class** of immunoglobulin that efficiently crosses the placenta into the fetal circulation, meaning that any present **IgG anti-A or anti-B antibodies** are the ones responsible for causing **fetal red cell hemolysis** in ABO incompatibility. Though ABO HDN is usually less severe than Rh HDN, the pathology depends entirely on the presence of IgG. *IgD*- IgD antibodies are primarily expressed on the surface of naïve **B lymphocytes** and are involved in B cell activation and signaling. They are not involved in **red blood cell agglutination** or placental transfer relevant to ABO incompatibility. [Practice more Pathology PYQs on OnCourse]

Q: Which of the following is the investigation of choice for CML?

Karyotyping. ***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. [Practice more Pathology PYQs on OnCourse]

Q: 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?

Retinoblastoma. ***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. [Practice more Pathology PYQs on OnCourse]

Question 1

Which blood is transfused in a patient with a Bombay blood group?

Accepted Answer

O negative

Answer

A

Answer

AB

Answer

B

Question 2

A 27-year-old pregnant female in her first trimester presents to the OPD for a regular antenatal checkup. During blood type screening, potential ABO incompatibility is discussed. The healthcare provider explains that certain antibody types are less concerning than others during pregnancy. ABO incompatibility does not occur due to which antibody in her case?

Accepted Answer

IgM

Answer

IgG

Answer

IgD

Answer

IgA

Question 3

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?

Accepted Answer

A. IgE-mediated reaction

Answer

D. T cell-mediated response

Answer

B. IgG-mediated reaction

Answer

C. IgA-mediated hypersensitivity

Question 4

Which of the following is the investigation of choice for CML?

Accepted Answer

Karyotyping

Answer

LAP score

Answer

FISH

Answer

Molecular testing (BCR-ABL PCR)

Question 5

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?

Accepted Answer

Retinoblastoma

Answer

Optic nerve glioma

Answer

Rhabdomyosarcoma

Answer

Ocular melanoma

FMGE 2024 — Pathology