Hematopathology Practice Questions

Q: The direct Coombs test detects which of the following?

Antibodies in serum. ### Explanation The **Direct Coombs Test (Direct Antiglobulin Test - DAT)** is designed to detect **antibodies (IgG) or complement proteins** that are already bound to the **surface of Red Blood Cells (RBCs)** in vivo. **Why the correct answer is B (Note: Correction to provided key):** There appears to be a discrepancy in the provided key. In medical immunology: * **Direct Coombs Test:** Detects antibodies/complement **on the RBC surface**. * **Indirect Coombs Test:** Detects free, unbound antibodies **in the serum**. If the goal is to identify the mechanism of the *Direct* test, the target is the sensitized RBC. #### Analysis of Options: * **Option B (Correct Mechanism):** In conditions like Autoimmune Hemolytic Anemia (AIHA), antibodies coat the patient's RBCs. Adding "Coombs Reagent" (antihuman globulin) causes these cells to agglutinate, confirming the presence of surface-bound antibodies. * **Option D (Incorrect for Direct):** Detecting antibodies in the serum is the purpose of the **Indirect Coombs Test**, used for prenatal screening (Rh incompatibility) and cross-matching. * **Options A & C (Incorrect):** Coombs tests are designed to detect antibodies (immunoglobulins), not the antigens themselves. #### High-Yield Clinical Pearls for NEET-PG: 1. **Direct Coombs Test Applications:** Hemolytic Disease of the Newborn (HDN), Drug-induced hemolytic anemia, and Transfusion reactions. 2. **Indirect Coombs Test Applications:** Checking maternal blood for anti-Rh antibodies and pre-transfusion compatibility. 3. **Coombs Reagent:** It is **Antihuman Globulin (AHG)**, usually produced by immunizing rabbits against human IgG/complement. 4. **Key Distinction:** Direct = "In the body" (RBCs already coated); Indirect = "In the lab" (Serum tested against reagent RBCs).

Q: A 4-year-old boy has appeared listless during the past week. He exhibits irritability when his arms or legs are touched. In the past 2 days, large ecchymoses have appeared on the right thigh and left shoulder. CBC shows hemoglobin, 9.3 g/dL; hematocrit, 28.7%; MCV, 96 mm3; platelet count, 45,000/mm3; and WBC count, 13,990/mm3. Examination of the peripheral blood smear shows blasts that lack peroxidase positive granules, but contain PAS-positive aggregates and stain positively for deoxynucleotidyl transferase negative (TdT-). Flow cytometry shows the phenotype of blasts to be CD19+, CD3-, and sIg-. Which of the following is the most likely diagnosis?

Acute lymphoblastic leukemia. **Explanation:** The clinical presentation and laboratory findings are classic for **Acute Lymphoblastic Leukemia (ALL)**, the most common malignancy in children. **1. Why the Correct Answer is Right:** * **Clinical Presentation:** The child presents with signs of bone marrow failure: anemia (listlessness), thrombocytopenia (ecchymoses), and bone pain (irritability when touched), which is caused by leukemic infiltration of the periosteum. * **Morphology & Cytochemistry:** The blasts are **PAS-positive** (characteristic of lymphoblasts) and **Peroxidase-negative** (ruling out AML). * **Immunophenotyping:** The presence of **CD19** (a B-cell marker) and the absence of surface immunoglobulin (**sIg-**) confirms a **Pre-B cell lineage**. While most ALL cases are TdT positive, the combination of CD19+, CD3-, and PAS positivity strongly points to ALL over any other option. **2. Why Incorrect Options are Wrong:** * **B. Acute Myelogenous Leukemia (AML):** AML blasts typically show **Myeloperoxidase (MPO)** positivity and may contain Auer rods. They would express myeloid markers (CD13, CD33) rather than CD19. * **C. Chronic Lymphocytic Leukemia (CLL):** CLL is a disease of the elderly (median age >60) and involves mature-appearing lymphocytes, not blasts. * **D. Chronic Myelogenous Leukemia (CML):** CML typically presents with massive splenomegaly and a spectrum of maturing myeloid cells (myelocytes, metamyelocytes) rather than a predominance of PAS-positive blasts. **3. NEET-PG High-Yield Pearls:** * **Most common childhood cancer:** ALL (Peak age: 2–5 years). * **Best Prognostic Factor:** Age 1–10 years and WBC count <50,000/mm³. * **Cytogenetics:** t(12;21) has a **good** prognosis; t(9;22) [Philadelphia chromosome] has a **poor** prognosis in ALL. * **Common Sites of Relapse:** Testes and CNS (due to the blood-brain/blood-testis barrier).

Q: Pancytopenia with hypercellular bone marrow is seen in which of the following conditions?

Megaloblastic anemia. **Explanation:** The hallmark of **Megaloblastic Anemia** is "ineffective hematopoiesis." In this condition (usually due to Vitamin B12 or Folate deficiency), there is a defect in DNA synthesis while RNA synthesis remains intact. This leads to nuclear-cytoplasmic asynchrony, where cells grow large but cannot divide properly [1]. Consequently, the bone marrow is **hypercellular** because it is packed with megaloblasts, but these cells undergo intramedullary destruction (apoptosis) before reaching maturity. This results in a decrease in all three cell lines in the peripheral blood (**Pancytopenia**). **Analysis of Incorrect Options:** * **Paroxysmal Nocturnal Hemoglobinuria (PNH):** While PNH can present with pancytopenia, it is typically associated with a **hypocellular** marrow (often overlapping with Aplastic Anemia) or a normocellular marrow with erythroid hyperplasia if hemolysis is the primary feature. * **Acquired Aplastic Anemia:** This is the classic cause of pancytopenia, but the bone marrow is characteristically **hypocellular** (replaced by fat cells). * **Thalassemia:** This typically presents with microcytic hypochromic anemia and erythroid hyperplasia in the marrow, but it does not usually cause generalized pancytopenia. **High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis of Pancytopenia with Hypercellular Marrow:** Megaloblastic anemia, Myelodysplastic Syndrome (MDS), and Aleukemic Leukemia. * **Peripheral Smear:** Look for macro-ovalocytes and **hypersegmented neutrophils** (>5 lobes) [1]. * **Biochemical Markers:** Elevated LDH and Indirect Bilirubin (due to ineffective hematopoiesis/intramedullary hemolysis). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 593-594.

Q: What is the antibody responsible for heparin-induced thrombocytopenia?

Antiheparin/PF4 antibody. ### Explanation **Heparin-Induced Thrombocytopenia (HIT)** is a life-threatening clinico-pathological syndrome caused by an immune response to heparin therapy. **1. Why Option A is correct:** The pathogenesis of HIT (specifically Type II) involves the formation of IgG antibodies against a complex of **Heparin and Platelet Factor 4 (PF4)**. PF4 is a cationic protein released from the alpha-granules of activated platelets. When heparin (anionic) binds to PF4, it creates a neoantigen. The resulting **IgG-Heparin-PF4 immune complexes** bind to the **FcγRIIa receptors** on the surface of platelets. This leads to: * **Platelet Activation:** Causing the release of procoagulant microparticles (leading to thrombosis). * **Platelet Consumption:** Leading to thrombocytopenia. **2. Why the other options are incorrect:** * **Option B (PF2):** Platelet Factor 2 is involved in fibrinogen sensitization but has no role in the pathogenesis of HIT. * **Option C (GP IIb/IIIa):** These are targets for antibodies in **Immune Thrombocytopenic Purpura (ITP)** and are the site of action for drugs like Abciximab. * **Option D (GP Ib/IX):** This is the Von Willebrand Factor (vWF) receptor. Deficiencies lead to **Bernard-Soulier Syndrome**, and it is also a target in some cases of ITP, but not HIT. **3. High-Yield Clinical Pearls for NEET-PG:** * **Timing:** Typically occurs **5–10 days** after starting heparin. * **Paradox:** Despite low platelet counts, HIT is a **pro-thrombotic state** (venous > arterial thrombosis). * **Diagnosis:** Screen with ELISA (high sensitivity); confirm with **Serotonin Release Assay (SRA)** (Gold Standard/High specificity). * **Management:** Immediately stop all heparin. Start alternative anticoagulants like **Argatroban** (Direct Thrombin Inhibitor) or Fondaparinux. Never give platelet transfusions as they "fuel the fire."

Q: What is the level of soluble transferrin receptor in iron deficiency anemia?

Increased. **Explanation:** **1. Why the Correct Answer (A) is Right:** Soluble Transferrin Receptor (sTfR) is a truncated form of the membrane-bound transferrin receptor found on the surface of erythroid precursor cells. Its concentration in the serum is directly proportional to the total number of transferrin receptors on these cells [1]. When intracellular iron levels drop—as seen in **Iron Deficiency Anemia (IDA)**—the cell upregulates the expression of transferrin receptors to capture as much iron as possible from the circulation [1]. Consequently, the level of sTfR increases significantly. This makes sTfR a sensitive marker for iron-deficient erythropoiesis. **2. Why Other Options are Wrong:** * **B. Decreased:** sTfR levels decrease in conditions where erythropoiesis is suppressed (e.g., aplastic anemia or chronic renal failure) or in states of iron overload (e.g., hemochromatosis), where cells downregulate receptors. * **C. Normal:** sTfR levels remain **normal in Anemia of Chronic Disease (ACD)**. This is the most critical clinical distinction, as ACD is characterized by iron sequestration rather than a true systemic deficit [1]. **3. NEET-PG High-Yield Pearls:** * **The "Gold Standard" Utility:** The sTfR assay is the most reliable test to differentiate between **IDA (Increased sTfR)** and **ACD (Normal sTfR)**, especially when ferritin levels are falsely elevated due to inflammation (as ferritin is an acute-phase reactant). * **sTfR-Ferritin Index:** A high index (sTfR/log Ferritin) is highly suggestive of IDA. * **Independence:** Unlike ferritin, sTfR levels are **not** affected by systemic inflammation, infection, or liver disease, making it a "cleaner" marker for marrow iron status. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 657-658.

Question 1

The RBC morphology in a peripheral blood smear in thalassemia trait resembles that of which condition?

Accepted Answer

Iron deficiency anemia

Answer

Vitamin B12 deficiency anemia

Answer

Folate deficiency anemia

Answer

Hereditary spherocytosis

Question 2

Cyclin D1/IgH gene rearrangement is associated with which of the following malignancies?

Accepted Answer

Mantle cell lymphoma

Answer

Hairy cell leukemia

Answer

Follicular lymphoma

Answer

Diffuse large B-cell lymphoma

Question 3

Sideroblasts are seen in all conditions except?

Accepted Answer

Thalassemia

Answer

Myelofibrosis

Answer

Alcoholism

Answer

Iron overload

Question 4

The direct Coombs test detects which of the following?

Accepted Answer

Antibodies in serum

Answer

Antigens in serum

Answer

Antibodies on the RBC surface

Answer

Antigens on the RBC surface

Question 5

A 4-year-old boy has appeared listless during the past week. He exhibits irritability when his arms or legs are touched. In the past 2 days, large ecchymoses have appeared on the right thigh and left shoulder. CBC shows hemoglobin, 9.3 g/dL; hematocrit, 28.7%; MCV, 96 mm3; platelet count, 45,000/mm3; and WBC count, 13,990/mm3. Examination of the peripheral blood smear shows blasts that lack peroxidase positive granules, but contain PAS-positive aggregates and stain positively for deoxynucleotidyl transferase negative (TdT-). Flow cytometry shows the phenotype of blasts to be CD19+, CD3-, and sIg-. Which of the following is the most likely diagnosis?

Accepted Answer

Acute lymphoblastic leukemia

Answer

Acute myelogenous leukemia

Answer

Chronic lymphocytic leukemia

Answer

Chronic myelogenous leukemia

Question 6

Pancytopenia with hypercellular bone marrow is seen in which of the following conditions?

Accepted Answer

Megaloblastic anemia

Answer

Paroxysmal nocturnal hemoglobinuria (PNH)

Answer

Acquired aplastic anemia

Answer

Thalassemia

Question 7

What is the antibody responsible for heparin-induced thrombocytopenia?

Accepted Answer

Antiheparin/PF4 antibody

Answer

Antiheparin/PF2 antibody

Answer

Antiheparin/GP IIb/IIIa antibody

Answer

Antiheparin GP Ib/IX antibody

Question 8

Which of the following is a cause of extravascular hemolysis?

Accepted Answer

Sickle cell disease

Answer

Falciparum malaria

Answer

Mismatched blood transfusion

Answer

Microthrombi in circulation

Question 9

In acute myeloid leukemia, Auer rods are numerous in which subtype?

Accepted Answer

M3

Answer

M2

Answer

M4

Answer

M5

Question 10

What is the level of soluble transferrin receptor in iron deficiency anemia?

Accepted Answer

Increased

Answer

Decreased

Answer

Normal

Answer

None

Hematopathology — MCQs

Hematopathology — MCQs

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