Hemoglobinopathies — MCQs
Which of the following is the most sensitive and specific test during antenatal check-up for a pregnant lady with family history of Thalassemia?
An 18-year-old man recently diagnosed with beta-thalassemia minor has a hemoglobin level of 10.5 g/dL and feels well. Which of the following findings is characteristic of this condition?
A 25-year-old lady presented with anemia, jaundice, and recurrent joint pains. All of the following are true except:
What is the major hemoglobin present in an adult?
Which of the following is not seen on hemoglobin electrophoresis in sickle cell anemia?
Fetomaternal transfusion of fetal RBCs in mother can be detected by: UPSC 08; TN 08; AIIMS 10
Which of the following statements about sickle cell disease is true?
The technique shown in the image is:
In G6PD deficiency, which enzyme's function is MOST directly impaired due to decreased NADPH availability, leading to reduced protection against oxidative stress?
OATP 1B1/2 gene mutation is seen in which of the following conditions?
Hemoglobinopathies Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is the most sensitive and specific test during antenatal check-up for a pregnant lady with family history of Thalassemia?
- A. P. smear and reticulocyte count
- B. Hemoglobin electrophoresis
- C. High performance liquid chromatography (Correct Answer)
- D. NESTROFT
Explanation: ***High performance liquid chromatography*** - **HPLC** is considered the most sensitive and specific test for diagnosing thalassemia and other hemoglobinopathies due to its ability to accurately quantify different hemoglobin fractions. - It provides a detailed **hemoglobin profile**, allowing for precise identification of abnormal hemoglobins and accurate assessment of thalassemia carrier status. *P. smear and reticulocyte count* - A **peripheral smear** can show microcytic, hypochromic red blood cells, which are characteristic of thalassemia, but this finding is not specific. - A **reticulocyte count** can indicate increased red blood cell production, but it is a general indicator of hemolysis or bone marrow activity and not specific for thalassemia. *Hemoglobin electrophoresis* - **Hemoglobin electrophoresis** separates different hemoglobin types based on their electrical charge, which is useful for identifying hemoglobinopathies. - While it can detect abnormal hemoglobins, its resolution and quantitative accuracy are generally lower than that of HPLC, making it less sensitive for detecting subtle variations or quantifying small amounts of abnormal hemoglobin. *NESTROFT* - **NESTROFT** (Naked eye single tube red cell osmotic fragility test) is a screening test used to detect beta-thalassemia carriers by assessing red cell osmotic fragility. - It is a good, inexpensive screening tool but lacks the sensitivity and specificity of definitive diagnostic tests like HPLC, and positive results require confirmation with other methods.
Question 2: An 18-year-old man recently diagnosed with beta-thalassemia minor has a hemoglobin level of 10.5 g/dL and feels well. Which of the following findings is characteristic of this condition?
- A. an increased amount of fetal hemoglobin (HbF) and hemoglobin A2 (HbA2) (Correct Answer)
- B. increased osmotic fragility of red blood cells
- C. normal bone marrow iron stores
- D. increased macroglobulins in the serum
Explanation: ***an increased amount of fetal hemoglobin (HbF) and hemoglobin A2 (HbA2)*** - Beta-thalassemia minor is characterized by a reduced synthesis of the **beta-globin chain**, leading to a relative increase in the proportions of **HbA2** and sometimes **HbF** as compensatory mechanisms [1]. - An elevated **HbA2** level, typically above 3.5%, is the **hallmark diagnostic feature** for beta-thalassemia trait/minor. *increased osmotic fragility of red blood cells* - **Increased osmotic fragility** is characteristic of conditions like **hereditary spherocytosis**, where red blood cells are more susceptible to lysis in hypotonic solutions [2]. - In beta-thalassemia, red blood cells are typically **microcytic and hypochromic** but do not usually show increased osmotic fragility; in fact, they may have *decreased* fragility due to structural changes. *normal bone marrow iron stores* - In thalassemia syndromes, a primary issue is defective globin synthesis, not iron deficiency; thus, **bone marrow iron stores are typically normal or even increased** due to ineffective erythropoiesis and repeated transfusions (in severe cases). - This contrasts with **iron deficiency anemia**, where bone marrow iron stores would be depleted, making this option incorrect as a *characteristic* differentiator of beta-thalassemia minor from other anemias where iron stores can be affected. *increased macroglobulins in the serum* - **Increased macroglobulins** (e.g., IgM antibodies) in the serum is characteristic of conditions like **Waldenström macroglobulinemia**, a type of B-cell lymphoma. - This finding has **no direct association** with beta-thalassemia minor, which is an inherited disorder of hemoglobin synthesis.
Question 3: A 25-year-old lady presented with anemia, jaundice, and recurrent joint pains. All of the following are true except:
- A. HbA will be undetectable
- B. She may have retinopathy
- C. Hydroxyurea would help her
- D. She can present with pulmonary bleeds (Correct Answer)
Explanation: ***She can present with pulmonary bleeds*** - The symptoms of **anemia**, **jaundice**, and recurrent **joint pains** in a 25-year-old suggest **sickle cell anemia**. Pulmonary bleeds are not a typical or common presentation of sickle cell disease; rather, patients are more prone to **acute chest syndrome**, which involves pulmonary infiltrates, but not usually frank bleeding [2]. - While various complications can affect the lungs in sickle cell disease, **pulmonary hemorrhage** is rare and not a characteristic feature. *HbA will be undetectable* - In **sickle cell anemia (Hb SS)**, the body exclusively produces **hemoglobin S (HbS)**, meaning **adult hemoglobin (HbA)**, the normal form, is indeed undetectable [3], [4]. - This is because the patient is homozygous for the **sickle gene**, preventing the synthesis of normal beta-globin chains [4]. *She may have retinopathy* - **Sickle cell retinopathy** is a common complication due to **vaso-occlusion** in the retinal vessels, leading to ischemia, neovascularization, and potentially vision loss. - This can manifest as various stages of proliferative retinopathy, often requiring treatment to preserve vision. *Hydroxyurea would help her* - **Hydroxyurea** is a medication used to reduce the frequency and severity of **sickle cell crises** and mitigate complications [1]. - It works by increasing the production of **fetal hemoglobin (HbF)**, which interferes with the polymerization of HbS and improves red blood cell function [1].
Question 4: What is the major hemoglobin present in an adult?
- A. HbA2
- B. HbA (Correct Answer)
- C. HbA1c
- D. HbA1b
Explanation: ***HbA*** - **Hemoglobin A (HbA)** is the primary and most abundant form of hemoglobin found in healthy adult red blood cells, constituting about 95-98% of total hemoglobin. - It consists of two **alpha (α)** and two **beta (β)** globin chains (α2β2). *HbA2* - **Hemoglobin A2 (HbA2)** is a minor adult hemoglobin, making up only about 2-3% of total hemoglobin in adults. - It is composed of two **alpha (α)** and two **delta (δ)** globin chains (α2δ2). *HbA1c* - **Hemoglobin A1c (HbA1c)** is a glycated form of HbA, where glucose molecules are irreversibly bound to the N-terminus of the beta globin chains. - While present in adults, its proportion reflects average blood glucose levels over the past 2-3 months and is not the major form of hemoglobin. *HbA1b* - **HbA1b** is another minor glycated hemoglobin component, similar to HbA1c but present in even smaller quantities. - It is a subset of the HbA1 fraction and does not represent the major adult hemoglobin.
Question 5: Which of the following is not seen on hemoglobin electrophoresis in sickle cell anemia?
- A. HbF
- B. HbS
- C. HbA (Correct Answer)
- D. HbA2
Explanation: ***HbA*** - Sickle cell anemia is characterized by the production of **HbS** (sickle hemoglobin) instead of **HbA** [1]. - Patients with sickle cell anemia typically have a significant reduction or absence of **HbA**, as it is replaced by HbS [1]. *HbA2* - **HbA2** is usually present in normal individuals and may be slightly increased in sickle cell disease but is not absent. - It is made up of **2 alpha and 2 delta chains** and does not directly correlate with sickle cell pathology. *HbF* - **HbF** (fetal hemoglobin) can actually be elevated in sickle cell anemia, helping to reduce sickling episodes. - Patients may have some level of **HbF**, which provides a degree of protection against the effects of sickle hemoglobin. *HbS* - **HbS** is the primary hemoglobin present in sickle cell anemia, leading to characteristic sickling of red blood cells [1][2]. - It is essential for the diagnosis of sickle cell disease, and its presence is confirmed during hemoglobin electrophoresis [1]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 598-599. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 599-600.
Question 6: Fetomaternal transfusion of fetal RBCs in mother can be detected by: UPSC 08; TN 08; AIIMS 10
- A. Electrophoresis
- B. Indirect Coomb's test
- C. Direct Coomb's test
- D. Betke-Kleihauer test (Correct Answer)
Explanation: ***Betke-Kleihauer test*** - The **Kleihauer-Betke test** (or acid elution test) detects fetal hemoglobin (HbF) in maternal blood. Fetal red blood cells, which contain HbF, are more resistant to acid elution and retain their hemoglobin, appearing stained, while adult red blood cells containing HbA lose their hemoglobin and appear as 'ghost' cells. - This visual differentiation allows for the quantification of **fetomaternal hemorrhage**, which is crucial for determining the appropriate dose of anti-D immunoglobulin in Rh-negative mothers [1]. - This is the **gold standard test** for detecting and quantifying fetomaternal transfusion. *Electrophoresis* - **Hemoglobin electrophoresis** is used to identify and quantify different types of hemoglobin (e.g., HbA, HbS, HbC, HbF) in a blood sample. While it can detect HbF, it is not the primary or most practical method for routinely quantifying the small percentage of fetal cells in maternal circulation in the context of fetomaternal hemorrhage. - It is typically used for diagnosing **hemoglobinopathies** and thalassemias, not for accurately determining the extent of fetomaternal transfusion. *Indirect Coombs test* - The **Indirect Coombs Test** (ICT) detects *antibodies circulating in the serum* that are capable of binding to red blood cells [1]. It is commonly used for **antibody screening** in prenatal care and for cross-matching blood transfusions. - While it can screen for maternal antibodies against fetal red blood cell antigens, it does not directly quantify the volume of fetal blood that has entered the maternal circulation. *Direct Coombs test* - The **Direct Coombs Test** (DCT) detects antibodies *attached directly to the surface of red blood cells*, typically indicating autoimmune hemolytic anemia or a hemolytic transfusion reaction. - It is used to detect antibodies on the infant's red blood cells in cases of **hemolytic disease of the newborn**, but not to quantify fetal cells in the mother's circulation. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 469-470.
Question 7: Which of the following statements about sickle cell disease is true?
- A. Sickling is completely reversible with oxygenation, making it clinically insignificant.
- B. Sickling leads to a significant increase in overall MCHC levels in the blood.
- C. Fetal hemoglobin inhibits sickling. (Correct Answer)
- D. Sickling occurs exclusively in the homozygous state and never in the heterozygous state.
Explanation: ***Sickling is reversible with oxygenation*** - When oxygen tension is restored, hemoglobin S can re-hydrate and revert to its normal shape, reducing sickling. - This reversible process is essential for managing episodes of vaso-occlusive crisis in sickle cell disease. *Fetal hemoglobin facilitates Sickling* - Fetal hemoglobin (HbF) actually inhibits sickling by stabilizing the erythrocyte shape and reducing the proportion of hemoglobin S [1]. - Individuals with higher levels of HbF experience fewer sickling-related complications [1]. *Sickling occurs both in heterozygous and homozygous state* - Sickling primarily occurs in the homozygous state (HbSS); heterozygotes (HbAS) usually do not experience significant sickling effects [1]. - Heterozygous individuals may have a selective advantage against malaria, but they are not prone to sickle cell crises. *Sickling Leads to decreased MCHC* - Sickling does not directly lead to decreased mean corpuscular hemoglobin concentration (MCHC); MCHC is typically normal in sickle cell patients. - In fact, sickle cell disease often results in hemolysis and can lead to increased MCHC in some cases.
Question 8: The technique shown in the image is:
- A. High performance liquid chromatography (Correct Answer)
- B. Haemoglobin electrophoresis
- C. Gel electrophoresis
- D. Tandem mass spectrometry
Explanation: ***High performance liquid chromatography*** - The image displays a **chromatogram** with distinct peaks labeled HbA1c, HbF, HbA0, and HbA2, separated based on their chemical properties. - This separation and detection method is characteristic of **High Performance Liquid Chromatography (HPLC)**, a technique used for quantifying different hemoglobin fractions. *Tandem mass spectrometry* - **Tandem mass spectrometry (MS/MS)** identifies compounds based on their mass-to-charge ratio and fragmentation patterns, which would look like mass spectra, not peaks on a time-based chromatogram. - While MS/MS is highly sensitive and specific, it doesn't produce the type of **elution profile** seen in the image. *Haemoglobin electrophoresis* - **Hemoglobin electrophoresis** separates hemoglobins based on their electrical charge, resulting in bands on a gel or a densitometric scan, not the **distinct chromatogram peaks** shown here. - While used for hemoglobin analysis, the visual representation is typically different, often displaying bands that reflect migration distance. *Gel electrophoresis* - **Gel electrophoresis** separates molecules, such as proteins or nucleic acids, by size and charge through a gel matrix, producing distinct **bands** that can be visualized. - This method would not produce the continuous **elution peaks over time** as observed in the provided graph, which indicates a liquid chromatography technique.
Question 9: In G6PD deficiency, which enzyme's function is MOST directly impaired due to decreased NADPH availability, leading to reduced protection against oxidative stress?
- A. Catalase
- B. Pyruvate kinase
- C. Superoxide dismutase
- D. Glutathione reductase (Correct Answer)
Explanation: ***Glutathione reductase*** - **G6PD deficiency** impairs the production of **NADPH** through the pentose phosphate pathway - **Glutathione reductase** is NADPH-dependent and reduces oxidized glutathione (GSSG) back to reduced glutathione (GSH) - Without adequate NADPH, glutathione reductase cannot maintain sufficient **GSH levels**, which is the primary antioxidant protecting RBCs from oxidative damage - This explains why G6PD deficiency leads to **hemolysis** when exposed to oxidative stressors (antimalarials, sulfonamides, fava beans) *Catalase* - **Catalase** decomposes hydrogen peroxide to water and oxygen, protecting cells from oxidative damage - While important for antioxidant defense, catalase does **not require NADPH** for its function - Its activity is not directly impaired by decreased NADPH in G6PD deficiency *Pyruvate kinase* - **Pyruvate kinase** catalyzes the final step of **glycolysis**, producing ATP - Its function is **completely independent** of NADPH levels - Pyruvate kinase deficiency causes a separate hemolytic anemia unrelated to oxidative stress or G6PD deficiency *Superoxide dismutase* - **Superoxide dismutase (SOD)** converts superoxide radicals to hydrogen peroxide and oxygen - SOD functions **independently of NADPH** and uses metal cofactors (Cu/Zn or Mn) - While part of antioxidant defense, it is not directly affected by G6PD deficiency
Question 10: OATP 1B1/2 gene mutation is seen in which of the following conditions?
- A. Gilbert syndrome
- B. Rotor syndrome (Correct Answer)
- C. Crigler Najjar syndrome
- D. Dubin Johnson syndrome
Explanation: **Explanation:** **Rotor Syndrome** is an autosomal recessive disorder characterized by chronic, conjugated (direct) hyperbilirubinemia. The molecular basis of this condition involves a **dual deficiency** of the hepatic uptake transporters **OATP1B1** and **OATP1B3** (encoded by the *SLCO1B1* and *SLCO1B3* genes). Under normal conditions, these transporters facilitate the re-uptake of conjugated bilirubin that has leaked into the sinusoidal blood back into the hepatocytes. When mutated, bilirubin cannot be re-absorbed, leading to elevated serum levels of conjugated bilirubin. **Analysis of Incorrect Options:** * **Gilbert Syndrome:** Caused by a mutation in the promoter region of the **UGT1A1** gene, leading to reduced activity of the bilirubin-glucuronosyltransferase enzyme. It results in mild, unconjugated hyperbilirubinemia. * **Crigler-Najjar Syndrome:** Caused by severe mutations in the **UGT1A1** gene. Type I involves a total absence of the enzyme, while Type II involves a severe deficiency. Both result in significant unconjugated hyperbilirubinemia. * **Dubin-Johnson Syndrome:** Caused by a mutation in the **MRP2** (ABCC2) gene, which encodes the canalicular multispecific organic anion transporter. This prevents the excretion of conjugated bilirubin into the bile, leading to a characteristic **black liver** due to melanin-like pigment accumulation. **High-Yield Clinical Pearls for NEET-PG:** * **Rotor vs. Dubin-Johnson:** In Rotor syndrome, the liver is **not** pigmented (normal appearance), and the total urinary coproporphyrin levels are elevated (with <70% being coproporphyrin I). * **Oral Cholecystography:** The gallbladder is usually visualized in Rotor syndrome but **not** in Dubin-Johnson syndrome. * **OATP1B1 Importance:** This transporter is also responsible for the hepatic uptake of **Statins**; mutations can increase the risk of statin-induced myopathy.
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