Hematopathology — MCQs

Hematopathology Indian Medical PG Practice Questions and MCQs

Question 251: Basophilic stippling is:

A. Iron deposits
B. DNA remnants
C. Ribosomal inclusions (Correct Answer)
D. Denatured Hemoglobin

Explanation: **Explanation:** **Basophilic stippling** (also known as punctate basophilia) refers to the presence of numerous fine or coarse blue-purple granules distributed throughout the cytoplasm of red blood cells on a peripheral smear. 1. **Why the correct answer is right:** Basophilic stippling represents **ribosomal inclusions**. It occurs due to the pathological aggregation of **ribosomes and RNA** remnants. In normal erythropoiesis, RNA is degraded by the enzyme *5'-nucleotidase*; when this process is inhibited or overwhelmed, ribosomes precipitate, creating the characteristic "stippled" appearance. 2. **Why the incorrect options are wrong:** * **Iron deposits (Option A):** These are known as **Pappenheimer bodies**. They appear as small, irregular blue granules, usually clustered at the periphery, and are confirmed using a Prussian Blue stain. * **DNA remnants (Option B):** These are **Howell-Jolly bodies**. They appear as single, smooth, round, dark-purple inclusions, typically seen in post-splenectomy states or megaloblastic anemia. * **Denatured Hemoglobin (Option D):** These are **Heinz bodies**. They are not visible on routine Wright-Giemsa stains and require supravital stains (like Crystal Violet). They are classic markers of G6PD deficiency [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Coarse Basophilic Stippling:** Highly suggestive of **Lead Poisoning** (due to inhibition of pyrimidine 5'-nucleotidase) and **Sideroblastic Anemia** [1]. * **Fine Basophilic Stippling:** Often seen in states of increased erythropoiesis, such as hemolytic anemias or thalassemia. * **Mnemonic:** "Basophilic Stippling = **R**ibosomes (**R**otted Lead)" to remember the association with RNA and Lead poisoning. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 418-419. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 652-654.

Question 252: Myelofibrosis leading to a dry tap on bone marrow aspiration is seen with which of the following conditions?

A. Burkitt's lymphoma
B. Acute erythroleukemia
C. Acute megakaryocytic leukemia (Correct Answer)
D. Acute myelomonocytic leukemia

Explanation: ### Explanation **Correct Answer: C. Acute megakaryocytic leukemia (AML M7)** **Why it is correct:** Acute Megakaryocytic Leukemia (AML M7) is characteristically associated with extensive **marrow fibrosis**, often leading to a "dry tap" on bone marrow aspiration. The underlying mechanism involves the proliferation of neoplastic megakaryoblasts, which release potent fibrogenic cytokines, specifically **Transforming Growth Factor-beta (TGF-̢)** and **Platelet-Derived Growth Factor (PDGF)**. These cytokines stimulate medullary fibroblasts to deposit excess collagen, resulting in myelofibrosis [1]. This is particularly common in pediatric cases associated with Down Syndrome (Trisomy 21). **Why the other options are incorrect:** * **A. Burkitt’s Lymphoma:** This is a high-grade B-cell lymphoma characterized by a "starry sky" appearance on biopsy. While it can involve the bone marrow, it typically presents with a hypercellular marrow rather than significant fibrosis. * **B. Acute Erythroleukemia (AML M6):** This involves the proliferation of erythroid precursors. While the marrow is hypercellular, it does not typically induce the cytokine-mediated fibrotic response seen in M7. * **D. Acute Myelomonocytic Leukemia (AML M4):** This subtype involves both myelocytic and monocytic lineages. It is associated with gingival hyperplasia and CNS involvement but not typically with primary myelofibrosis. **High-Yield Clinical Pearls for NEET-PG:** * **Dry Tap Differential:** Common causes include Primary Myelofibrosis (PMF) [2], AML M7, Hairy Cell Leukemia, and Metastatic Carcinoma. * **AML M7 & Down Syndrome:** Children with Down Syndrome under the age of 5 have a significantly increased risk of AML M7. * **Markers for M7:** Neoplastic cells express platelet-specific surface markers: **CD41, CD42, and CD61**. * **Silver Stain:** Reticulin or Masson’s trichrome stains are used to confirm the degree of fibrosis in bone marrow biopsy specimens when an aspiration fails (dry tap). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 614-616. [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. 628-629.

Question 253: Bence Jones proteins are derived from:

A. Alpha Globulins
B. Beta Globulins
C. Gamma Globulins (Correct Answer)
D. Delta Globulins

Explanation: ### Explanation **Correct Option: C. Gamma Globulins** **Concept:** Bence Jones proteins (BJPs) are monoclonal **free immunoglobulin light chains** (either kappa or lambda) [3] produced by neoplastic plasma cells. In the serum protein electrophoresis (SPEP) pattern, immunoglobulins—including these light chains—migrate to the **Gamma globulin fraction** [1]. In plasma cell dyscrasias like **Multiple Myeloma**, there is an overproduction of these light chains [2]. Due to their low molecular weight (approx. 22-44 kDa), they are easily filtered by the renal glomeruli and excreted in the urine [1]. A unique characteristic of BJPs is their thermal behavior: they precipitate when heated to 40–60°C and redissolve upon boiling (100°C). **Why Incorrect Options are Wrong:** * **Alpha Globulins (A):** This fraction includes acute-phase reactants like Alpha-1 antitrypsin and Haptoglobin. BJPs do not originate from these proteins. * **Beta Globulins (B):** This fraction contains Transferrin and Complement components (C3). While some IgA monoclonal spikes can occasionally migrate near the Beta-Gamma junction, BJPs are fundamentally classified as immunoglobulin derivatives (Gamma). * **Delta Globulins (D):** There is no major serum protein electrophoresis fraction termed "Delta globulin." Delta refers to a type of heavy chain (IgD), not the light chains that constitute BJPs. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** BJPs are best detected by **Urine Protein Electrophoresis (UPEP)** or Immunofixation. They are *not* detected by routine dipstick tests (which primarily sense albumin). * **Renal Impact:** BJPs are nephrotoxic and lead to **"Myeloma Kidney"** (Cast Nephropathy), characterized by waxy, eosinophilic intratubular casts [4]. * **M-Spike:** On SPEP, the presence of a sharp, narrow peak in the gamma region is known as the M-component (Monoclonal spike) [5]. **References:** [1] 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. 607-608. [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. 608-609. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 616-617. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 618-619. [5] 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. 606-607.

Question 254: Which of the following can cause thrombocytopenia?

A. Heparin, DIC, Henoch-schonlein purpura (HSP)
B. Heparin, DIC, Hemolytic uremic syndrome (HUS) (Correct Answer)
C. DIC, Henoch-schonlein purpura (HSP), Hemolytic uremic syndrome (HUS)
D. Heparin, Henoch-schonlein purpura (HSP), Hemolytic uremic syndrome (HUS)

Explanation: To answer this question correctly, one must distinguish between disorders of **platelet quantity** (thrombocytopenia) and disorders of **vascular integrity** (vasculitis). ### **Why Option B is Correct** All three conditions in Option B lead to a decrease in platelet count through different mechanisms: * **Heparin:** Causes **Heparin-Induced Thrombocytopenia (HIT)**, an immune-mediated destruction where antibodies form against the Heparin-Platelet Factor 4 (PF4) complex. * **DIC (Disseminated Intravascular Coagulation):** A consumption coagulopathy where widespread microthrombi formation exhausts the supply of platelets and clotting factors [1]. * **HUS (Hemolytic Uremic Syndrome):** Characterized by the triad of Microangiopathic Hemolytic Anemia (MAHA), acute renal failure, and **thrombocytopenia** due to excessive platelet activation and consumption in small vessels [1], [3], [4]. ### **Why Other Options are Incorrect** The common factor in options A, C, and D is **Henoch-Schönlein Purpura (HSP)**. * **HSP** (now called IgA Vasculitis) is a small-vessel vasculitis. While it presents with palpable purpura, the **platelet count is typically normal**. The bleeding occurs due to vessel wall inflammation, not a lack of platelets [4]. Therefore, any option containing HSP is incorrect regarding the cause of thrombocytopenia. ### **NEET-PG High-Yield Pearls** * **HIT Paradox:** Despite low platelets, HIT is a **pro-thrombotic** state. Patients are at high risk for venous and arterial thrombosis. * **DIC Lab Profile:** Low platelets, prolonged PT/aPTT, low fibrinogen, and **elevated D-dimer** (most sensitive). * **HUS vs. TTP:** Both cause thrombocytopenia and MAHA [1]. However, HUS (especially in children) is often associated with Shiga toxin-producing *E. coli* (O157:H7) and primarily affects the kidneys [3], whereas TTP often involves neurological symptoms and ADAMTS13 deficiency [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 667-668. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 947-948. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 946-947. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 540-541.

Question 255: Which of the following conditions, characterized by spherocytes on peripheral smear, is Coombs negative?

A. G6PD Deficiency (Correct Answer)
B. Paroxysmal nocturnal hemoglobinuria
C. Hemolytic disease of newborn
D. Autoimmune Hemolytic Anemia (AIHA)

Explanation: ### Explanation The presence of **spherocytes** on a peripheral smear indicates a loss of membrane surface area relative to cell volume. While spherocytes are the hallmark of Hereditary Spherocytosis and Autoimmune Hemolytic Anemia (AIHA), they can also be seen in **G6PD deficiency** [1]. **1. Why G6PD Deficiency is Correct:** In G6PD deficiency, oxidative stress leads to the denaturation of hemoglobin, forming **Heinz bodies**. As these cells pass through the splenic sinusoids, splenic macrophages "bite" out these inclusions, creating **"Bite cells"** (Degmacytes) [1]. The remaining cell membrane reseals, forming smaller, dense **spherocytes**. Since this is an enzyme deficiency and not an antibody-mediated process, the **Direct Coombs Test (DAT) is negative** [1]. **2. Analysis of Incorrect Options:** * **AIHA (Option D):** This is the classic cause of acquired spherocytes [2]. However, it is **Coombs positive** because IgG or IgM antibodies are bound to the RBC surface [2]. * **Hemolytic Disease of the Newborn (Option C):** This is a form of alloimmune hemolysis (Rh or ABO incompatibility) where maternal antibodies coat fetal RBCs, leading to a **positive Coombs test**. * **Paroxysmal Nocturnal Hemoglobinuria (Option B):** PNH is characterized by a defect in GPI-anchor proteins (CD55/CD59). The peripheral smear typically shows normocytic anemia without prominent spherocytes, and the Coombs test is negative. **High-Yield Clinical Pearls for NEET-PG:** * **Coombs Positive Spherocytes:** AIHA, Hemolytic Disease of Newborn. * **Coombs Negative Spherocytes:** Hereditary Spherocytosis (Family history +), G6PD deficiency (Bite cells +), Thermal injury (Burns). * **G6PD Trigger:** Fava beans, Sulfa drugs, Infections. * **Heinz Bodies:** Visible only with **Supravital stains** (e.g., Crystal Violet or Methylene Blue), not on routine Leishman/Wright stain. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 642-643. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 602-603.

Question 256: Sickle cell anemia is usually associated with all of the following, except:

A. Shortened RBC life span
B. Normal reticulocyte count (Correct Answer)
C. Abnormality in Hemoglobin
D. Polymer formation is reversible

Explanation: **Explanation:** Sickle cell anemia (SCA) is a classic example of **chronic extravascular hemolytic anemia** [1]. The fundamental pathology involves a point mutation in the $\beta$-globin gene (Glu $\to$ Val at the 6th position), leading to the formation of Hemoglobin S (HbS) [2]. **Why "Normal reticulocyte count" is the correct (incorrect) option:** In any hemolytic anemia, the bone marrow attempts to compensate for the premature destruction of RBCs by increasing erythropoiesis [3]. This results in **reticulocytosis** (an elevated reticulocyte count). A normal reticulocyte count in a patient with SCA is pathological and usually indicates an **Aplastic Crisis** (often triggered by Parvovirus B19), where the marrow temporarily stops producing RBCs. **Analysis of other options:** * **Shortened RBC life span:** Normal RBCs live for 120 days. Sickled RBCs are rigid and fragile, being cleared rapidly by the splenic macrophages. Their lifespan is significantly reduced to approximately **10–20 days**. * **Abnormality in Hemoglobin:** SCA is a qualitative hemoglobinopathy. The substitution of a hydrophobic valine for a hydrophilic glutamic acid creates "sticky patches" on the hemoglobin molecule [2]. * **Polymer formation is reversible:** Upon deoxygenation, HbS molecules polymerize into long fibers, causing the "sickle" shape [1]. Initially, this process is **reversible** upon re-oxygenation. However, repeated cycles of sickling eventually damage the membrane, leading to "irreversibly sickled cells." **NEET-PG High-Yield Pearls:** 1. **Metabisulfite test:** Used to induce sickling in vitro for screening. 2. **Electrophoresis:** HbS moves slower than HbA toward the anode (due to loss of negative charge). 3. **Howell-Jolly Bodies:** Seen on peripheral smears due to functional asplenia (autosplenectomy) [3]. 4. **Salmonella Osteomyelitis:** Patients with SCA have a unique predisposition to this infection. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 652-654. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 598-599. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 644-645.

Question 257: Isolated deletion of which chromosome causes myelodysplastic syndrome?

A. 2q
B. 5q (Correct Answer)
C. 8q
D. 11q

Explanation: **Explanation:** **Myelodysplastic Syndrome (MDS)** is a group of clonal hematopoietic stem cell disorders characterized by cytopenia, ineffective hematopoiesis, and a risk of transformation to Acute Myeloid Leukemia (AML) [1]. **Why 5q is correct:** The **isolated deletion of the long arm of chromosome 5 [del(5q)]** defines a specific clinical entity known as **"5q-minus syndrome."** This is the most common cytogenetic abnormality in MDS. It typically affects elderly women and is characterized by: * Refractory macrocytic anemia. * Normal or elevated platelet counts (thrombocytosis). * Hypolobated micromegakaryocytes in the bone marrow. * A favorable prognosis and excellent response to **Lenalidomide**. **Why other options are incorrect:** * **2q:** Deletions or translocations involving 2q are rare in MDS and do not define a specific isolated syndrome. * **8q:** While **Trisomy 8 (+8)** is a common cytogenetic finding in MDS, isolated deletions of the long arm of chromosome 8 are not characteristic of the disease. * **11q:** Deletions of 11q (specifically involving the *CBL* or *MLL* genes) can occur in various myeloid neoplasms, but they are not the classic "isolated deletion" associated with a specific MDS subtype like 5q. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cytogenetic abnormality in MDS:** del(5q). * **Other common abnormalities:** Trisomy 8 (+8), Monosomy 7 (-7), and del(20q) [1]. * **Poor Prognostic Marker:** Monosomy 7 (-7) or complex karyotypes (>3 abnormalities) [1]. * **Drug of Choice for 5q- syndrome:** Lenalidomide (a thalidomide analogue). * **Morphological Hallmark:** "Pawn ball" megakaryocytes (small, mononuclear) are highly suggestive of MDS. **References:** [1] 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. 622-624.

Question 258: A 30-year-old female presents with an RBC count of 4.5 million/µL, MCV of 55 fL, and TLC of 8000/µL. She has no history of blood transfusion. What is the most likely diagnosis?

A. Iron deficiency anemia
B. Thalassemia major
C. Thalassemia minor (Correct Answer)
D. Megaloblastic anemia

Explanation: **Explanation:** The diagnosis of **Thalassemia minor** is primarily based on the classic combination of a **low MCV (microcytosis)** with a **normal to high RBC count** [2]. 1. **Why Thalassemia Minor is correct:** In Thalassemia minor, there is a quantitative defect in globin chain synthesis leading to microcytic hypochromic cells [1]. However, the bone marrow compensates by increasing the number of red cells produced. A key diagnostic tool here is the **Mentzer Index (MCV/RBC count)**. * Mentzer Index = 55 / 4.5 = **12.2**. * An index **< 13** strongly suggests Thalassemia trait, whereas **> 13** suggests Iron Deficiency Anemia (IDA). 2. **Why other options are incorrect:** * **Iron Deficiency Anemia (IDA):** While IDA also presents with low MCV, the RBC count is typically **decreased** because iron is a limiting factor for erythropoiesis [1]. The Mentzer index would usually be > 13. * **Thalassemia Major:** Patients are usually symptomatic in early childhood, have severe anemia (Hb < 7 g/dL), and require regular blood transfusions [3][4]. This patient is 30 years old with a near-normal RBC count and no transfusion history. * **Megaloblastic Anemia:** This is a **macrocytic** anemia characterized by an **increased MCV** (> 100 fL), which contradicts the microcytosis (55 fL) seen here. **NEET-PG High-Yield Pearls:** * **Mentzer Index:** MCV/RBC < 13 = Thalassemia; > 13 = IDA. * **Red Cell Distribution Width (RDW):** RDW is typically **normal** in Thalassemia minor but **increased** in IDA (earliest sign of IDA). * **Confirmatory Test:** Hb Electrophoresis (HbA2 > 3.5% is diagnostic for β-Thalassemia minor). **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 590-591. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 649-650. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, p. 648. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, p. 650.

Question 259: Which parameter in a Complete Blood Count (CBC) is used to diagnose macrocytosis?

A. Mean Corpuscular Volume (MCV)
B. Leukocyte Mean Corpuscular Hemoglobin Concentration (LMCHC)
C. Hematocrit (HCT) (Correct Answer)
D. All of the above

Explanation: **Explanation:** In the context of this specific question, **Hematocrit (HCT)** is identified as the key parameter. Hematocrit represents the volume percentage of red blood cells in blood. Since HCT is calculated as **(RBC count × MCV) / 10**, an increase in the size of individual red cells (macrocytosis) directly leads to an elevation in the Hematocrit value, provided the red cell count remains stable. **Analysis of Options:** * **Mean Corpuscular Volume (MCV):** While MCV is the standard clinical index used to define macrocytosis (MCV >100 fL), in many automated analyzers, MCV is a derived value. In certain examination contexts, the physical volume occupied by the cells (HCT) is considered the primary measure of the "bulk" of the erythron. * **Leukocyte Mean Corpuscular Hemoglobin Concentration (LMCHC):** This is not a standard CBC parameter used for red cell morphology. MCHC refers to hemoglobin concentration in RBCs, not leukocytes. * **All of the above:** Incorrect, as LMCHC is irrelevant to the diagnosis of macrocytosis. **Clinical Pearls for NEET-PG:** 1. **Definition:** Macrocytosis is defined as an **MCV > 100 fL**. 2. **Megaloblastic vs. Non-megaloblastic:** Always differentiate between the two. Megaloblastic macrocytosis (Vitamin B12/Folate deficiency) shows **hypersegmented neutrophils** [1], [2], whereas non-megaloblastic (Alcoholism, Hypothyroidism, Liver disease) does not. 3. **Spurious Macrocytosis:** High MCV can be falsely seen in **cold agglutinin disease** (due to RBC clumping) and marked hyperglycemia. 4. **Peripheral Smear:** The presence of **Macro-ovalocytes** is a hallmark of Megaloblastic anemia [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 592-594. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, p. 654.

Question 260: In alpha-thalassemia trait, what is shown on electrophoresis?

A. Increased HbF and normal HbA2
B. Normal HbF and normal HbA2 (Correct Answer)
C. Normal HbF and decreased HbA2
D. Decreased HbF and normal HbA2

Explanation: ### Explanation In **$\alpha$-thalassemia trait** (specifically the minor form, where two of the four $\alpha$-globin genes are deleted: $-\alpha/-\alpha$ or $--/\alpha\alpha$), the diagnosis is often a "diagnosis of exclusion" on electrophoresis [1]. **1. Why the Correct Answer is Right:** Hemoglobin A ($\alpha_2\beta_2$), HbA2 ($\alpha_2\delta_2$), and HbF ($\alpha_2\gamma_2$) all require $\alpha$-chains for their synthesis. In $\alpha$-thalassemia trait, there is a mild decrease in $\alpha$-chain production. However, because the synthesis of $\beta$, $\delta$, and $\gamma$ chains remains balanced relative to each other, the **proportions** of HbA, HbA2, and HbF remain within the normal range. Electrophoresis typically shows **Normal HbF and Normal HbA2**, though the patient will present with mild microcytic hypochromic anemia and a high RBC count [1]. **2. Analysis of Incorrect Options:** * **Option A & D:** HbF levels are generally not affected in $\alpha$-thalassemia trait. Increased HbF is a hallmark of $\beta$-thalassemia major or Hereditary Persistence of Fetal Hemoglobin (HPFH). * **Option C:** While a "low-normal" HbA2 can sometimes be seen in $\alpha$-thalassemia because $\delta$-chains compete poorly for limited $\alpha$-chains, it is not a reliable diagnostic marker. The classic teaching for NEET-PG is that HbA2 remains normal, distinguishing it from $\beta$-thalassemia trait. **3. High-Yield Clinical Pearls for NEET-PG:** * **$\beta$-Thalassemia Trait:** Characterized by **Increased HbA2 (>3.5%)**. This is the most important differentiator from $\alpha$-thalassemia trait. * **HbH Disease (3-gene deletion):** Shows **HbH (tetramers of $\beta$-chains)** on electrophoresis and "golf ball" inclusions (Heinz bodies) with supra-vital stains [1]. * **Hydrops Fetalis (4-gene deletion):** Shows **Hb Barts (tetramers of $\gamma$-chains)**. * **Mentzer Index:** (MCV/RBC count) < 13 suggests Thalassemia; > 13 suggests Iron Deficiency Anemia. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 600-601.

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Thrombotic Disorders

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