Hemolytic Anemias — MCQs
Hemolysis is predominantly intravascular in which of the following conditions?
A patient with hemolytic anemia has a defect in the enzyme glucose-6-phosphate dehydrogenase. Which of the following pathways is directly affected by this defect?
Which is not a feature of G6PD deficiency?
Which of the following conditions is the classic example of acute intravascular hemolysis triggered by oxidative stress?
Direct Coombs test is positive in all EXCEPT:
Which type of immunoglobulin is primarily associated with cold agglutinin disease?
All of the following conditions are associated with Coombs-positive hemolytic anemia, except:
Which is NOT a feature of microangiopathic hemolytic anemia?
Splenectomy is least useful in
A 45-year-old male presents with fatigue, pale skin, and jaundice. Labs reveal hemolysis and a positive direct Coombs test. What is the most likely diagnosis?
Hemolytic Anemias Indian Medical PG Practice Questions and MCQs
Question 1: Hemolysis is predominantly intravascular in which of the following conditions?
- A. Paroxysmal nocturnal hemoglobinuria (Correct Answer)
- B. Warm autoimmune hemolytic anemia
- C. Cold autoimmune hemolytic anemia
- D. Spherocytosis
Explanation: ***Paroxysmal nocturnal hemoglobinuria*** - **PNH** is characterized by a defect in the **PIG-A gene**, leading to a deficiency of **GPI-anchored proteins** like CD55 and CD59 on red blood cells [1]. - This deficiency makes the red blood cells susceptible to complement-mediated lysis, predominantly occurring **intravascularly** [1]. *Warm autoimmune hemolytic anemia* - This condition involves **IgG autoantibodies** binding to red blood cells, which are then primarily removed by **macrophages in the spleen** and liver (extravascular hemolysis) [2]. - The presence of **spherocytes** and a positive direct **antiglobulin test (DAT)** are characteristic [2]. *Cold autoimmune hemolytic anemia* - Involves **IgM autoantibodies** that bind to red blood cells at colder temperatures, often causing agglutination in the peripheral circulation. - While some complement activation and lysis can occur intravascularly, the primary mechanism involves **macrophages in the liver** clearing antibody-coated red cells (extravascular), or red cell destruction in the cooler acral areas. *Spherocytosis* - This is a condition of abnormal red blood cell shape due to defects in **cytoskeletal proteins** (e.g., spectrin, ankyrin), making them less deformable. - These rigid spherocytes are primarily trapped and destroyed by the **phagocytic cells in the spleen**, indicating an **extravascular hemolytic process** [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. 650-651. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 602-603.
Question 2: A patient with hemolytic anemia has a defect in the enzyme glucose-6-phosphate dehydrogenase. Which of the following pathways is directly affected by this defect?
- A. Glycolysis
- B. Pentose phosphate pathway (Correct Answer)
- C. TCA cycle
- D. Urea cycle
Explanation: ***Pentose phosphate pathway*** - **Glucose-6-phosphate dehydrogenase (G6PD)** is the **rate-limiting enzyme** in the **pentose phosphate pathway (PPP)**, initiating the oxidative phase. - Deficiency in G6PD impairs the production of **NADPH**, which is crucial for reducing **oxidative stress** in red blood cells. *Glycolysis* - This pathway metabolizes glucose to pyruvate for **ATP production** and does not directly involve G6PD. - While G6P is an intermediate in both pathways, its conversion in glycolysis is catalyzed by phosphoglucose isomerase, not G6PD. *TCA cycle* - The **tricarboxylic acid (TCA) cycle** is a central metabolic pathway for energy production occurring in the **mitochondria**. - It involves the oxidation of acetyl-CoA and does not directly utilize G6PD. *Urea cycle* - The **urea cycle** is responsible for detoxifying ammonia by converting it into urea, primarily occurring in the **liver**. - This pathway is unrelated to glucose metabolism or G6PD activity.
Question 3: Which is not a feature of G6PD deficiency?
- A. Presence of Heinz bodies
- B. Males and females are equally affected (Correct Answer)
- C. Absence of NADPH
- D. Oxidative stress
Explanation: ***Males and females are equally affected*** - G6PD deficiency is an **X-linked recessive disorder**, meaning males are predominantly and more severely affected because they have only one X chromosome [2]. - Females are typically carriers and are less commonly affected, or may experience milder symptoms, due to **X-chromosome inactivation** (Lyonization). *Presence of Heinz bodies* - **Heinz bodies** are formed from denatured hemoglobin precipitates within red blood cells, a characteristic feature of **oxidative stress** in G6PD deficiency [2]. - These bodies are removed by the spleen, contributing to **hemolytic anemia**. *Absence of NADPH* - G6PD is the rate-limiting enzyme in the **pentose phosphate pathway**, which generates **NADPH** [1], [2]. - Without sufficient G6PD, the production of **NADPH** is severely impaired, leading to a deficiency in this critical reducing agent. *Oxidative stress* - **NADPH** is crucial for reducing **glutathione**, which in turn detoxifies reactive oxygen species [2]. - The lack of NADPH makes red blood cells vulnerable to **oxidative damage**, manifesting as hemolytic anemia upon exposure to oxidative agents [3].
Question 4: Which of the following conditions is the classic example of acute intravascular hemolysis triggered by oxidative stress?
- A. Hereditary spherocytosis
- B. Sickle cell disease
- C. Acute G6PD deficiency (Correct Answer)
- D. None of the options
Explanation: ***b and c*** - Intravascular hemolysis is commonly associated with both **Acute G6PD deficiency** and **Hereditary spherocytosis**, leading to destruction of red blood cells in the bloodstream [1]. - These conditions are characterized by **high levels of hemoglobinuria** and **low haptoglobin**, indicative of intravascular hemolysis. *Sickle cell ds* - Sickle cell disease primarily causes **extravascular hemolysis** due to splenic sequestration rather than **intravascular** destruction [3]. - The clinical features include **vaso-occlusive crises** and splenic infarction rather than hemolysis within the blood vessels. *Acute G6PD* - While acute G6PD deficiency can lead to hemolysis, it is typically **triggered by oxidative stress** rather than occurring continuously [2]. - The hemolysis in G6PD deficiency occurs more in an **extravascular** manner unless acute stress occurs, which can result in **acute intravascular hemolysis, marked by anemia, hemoglobinemia, and hemoglobinuria** [4]. *Hereditary spherocytosis* - This condition primarily causes **extravascular hemolysis** through the spleen, where abnormal spherocytes are destroyed [1]. - Although it leads to anemia, the hallmark of hereditary spherocytosis is the **spleen's role** in hemocyte destruction rather than intravascular hemolysis.
Question 5: Direct Coombs test is positive in all EXCEPT:
- A. G6PD deficiency (Correct Answer)
- B. Rh incompatibility
- C. Autoimmune hemolysis
- D. ABO incompatibility
Explanation: ***G6PD deficiency*** - **G6PD deficiency** is an intrinsic red blood cell defect that leads to hemolytic anemia, but it does **not involve immune-mediated destruction** of red blood cells. - The **Direct Coombs test** detects antibodies or complement components bound to the surface of red blood cells; since G6PD deficiency is not immune-mediated, the test will be negative. *Rh incompatibility* - **Rh incompatibility** occurs when maternal antibodies cross the placenta and target fetal red blood cells, leading to **immune-mediated hemolysis** [1]. - The anti-D antibodies bind to fetal red blood cells, resulting in a **positive Direct Coombs test** (detecting antibody-coated fetal RBCs) [1]. *Autoimmune hemolysis* - **Autoimmune hemolysis** involves the body producing **autoantibodies** against its own red blood cells, leading to their premature destruction [3]. - These autoantibodies (e.g., IgG, IgM) bind to the red blood cell surface, making the **Direct Coombs test positive** [3]. *ABO incompatibility* - **ABO incompatibility** involves the presence of naturally occurring antibodies (e.g., anti-A, anti-B) in a recipient's plasma that react with donor red blood cells [2]. - When incompatible red blood cells are transfused, or in cases of **hemolytic disease of the newborn** due to ABO incompatibility, antibodies bind to the RBCs, resulting in a **positive Direct Coombs test** [2].
Question 6: Which type of immunoglobulin is primarily associated with cold agglutinin disease?
- A. IgG
- B. IgM (Correct Answer)
- C. IgA
- D. IgD
Explanation: ***IgM*** - Cold agglutinins are primarily composed of **IgM antibodies** [1] which are produced in response to certain infections, notably Mycoplasma pneumoniae. - They can cause **cold agglutinin disease**, leading to hemolytic anemia when the blood is exposed to cooler temperatures [2]. *IgG* - While IgG is the most abundant antibody in blood, it is not responsible for cold agglutination. - IgG typically functions in **immune memory** and neutralization rather than agglutination at cold temperatures. *IgD* - IgD is mainly found on the surface of **B cells** and has a role in initiating B cell activation. - It plays a minimal role in the antibody response and does not participate in cold agglutination. *IgA* - IgA is primarily involved in mucosal immunity, found in secretions like saliva and tears. - It does not function as a cold agglutinin; hence, it is not associated with cold temperature-related agglutination. **References:** [1] 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. 154-155. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 651-652.
Question 7: All of the following conditions are associated with Coombs-positive hemolytic anemia, except:
- A. SLE
- B. Thrombotic Thrombocytopenic Purpura
- C. PAN (Correct Answer)
- D. Scleroderma
Explanation: ***PAN*** - **Polyarteritis nodosa (PAN)** is a **necrotizing vasculitis** that typically affects medium-sized arteries. It is not generally associated with Coombs-positive hemolytic anemia. - While systemic inflammation can cause anemia of chronic disease, direct autoantibody-mediated red blood cell destruction is not a feature of PAN. *Thrombotic Thrombocytopenic Purpura* - **Thrombotic thrombocytopenic purpura (TTP)** is characterized by microangiopathic hemolytic anemia, but it is typically **Coombs-negative** [3]. - The hemolysis in TTP is due to mechanical fragmentation of red blood cells as they pass through fibrin networks in small vessels, not antibody-mediated destruction [3]. *Scleroderma* - **Systemic sclerosis (scleroderma)** can be associated with autoimmune phenomena including **autoimmune hemolytic anemia**, which can be Coombs-positive [2]. - While less common than in SLE, autoimmune hemolytic anemia is a recognized complication in some patients with scleroderma due to immune dysregulation [2], [3]. *SLE* - **Systemic lupus erythematosus (SLE)** is frequently associated with **Coombs-positive hemolytic anemia** [1]. - **Autoantibodies** against red blood cell surface antigens are common in SLE, leading to their destruction by the immune system [1], [2].
Question 8: Which is NOT a feature of microangiopathic hemolytic anemia?
- A. Spherocytes (Correct Answer)
- B. High LDH
- C. Schistocytes
- D. Low haptoglobin
Explanation: ***Spherocytes*** - **Spherocytes** are typically found in conditions like **hereditary spherocytosis** or **autoimmune hemolytic anemia**, where red blood cells are damaged or improperly formed, leading to a spherical shape [1]. - In **microangiopathic hemolytic anemia (MAHA)**, red cells are fragmented by shear stress from damaged small blood vessels, resulting in **schistocytes**, not spherocytes. *High LDH* - **Lactate dehydrogenase (LDH)** is an intracellular enzyme released when red blood cells are destroyed, making **elevated LDH** a common finding in hemolytic anemias, including MAHA. - Its high levels reflect increased red cell turnover and destruction in the microvasculature. *Schistocytes* - **Schistocytes**, or fragmented red blood cells, are the **hallmark** of microangiopathic hemolytic anemia. - They are formed when red blood cells pass through damaged small blood vessels containing fibrin strands, leading to their shearing and destruction. *Low haptoglobin* - **Haptoglobin** is a plasma protein that binds free hemoglobin released during red blood cell destruction. - In hemolytic anemias like MAHA, there is increased hemoglobin release, which saturates and depletes haptoglobin, leading to **low or undetectable levels**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 602-603.
Question 9: Splenectomy is least useful in
- A. Hereditary nonspherocytic haemolytic anaemia (Correct Answer)
- B. Congenital elliptocytosis
- C. Thalassemia major
- D. Congenital spherocytic anaemia
Explanation: ***Hereditary nonspherocytic hemolytic anemia*** - This group of anemias primarily involves **defects in red blood cell enzymes**, such as G6PD deficiency or pyruvate kinase deficiency, leading to premature destruction of red blood cells (hemolysis) mainly in the **bone marrow** and peripheral circulation, not predominantly in the spleen. - Since the spleen is not the primary site of red blood cell destruction in these conditions, **splenectomy generally offers little to no benefit** and may even be contraindicated due to increased risks without significant clinical improvement. *Congenital elliptocytosis* - This condition involves **abnormalities in red blood cell membrane proteins**, leading to elliptical-shaped red blood cells that are more fragile and prone to splenic sequestration and destruction [1]. - **Splenectomy is a treatment option** for severe cases of congenital elliptocytosis, as it reduces splenic trapping and destruction of abnormal red blood cells, thereby alleviating anemia and hemolysis [1]. *Thalassemia major* - **Thalassemia major** is characterized by severe impairment of hemoglobin synthesis, leading to ineffective erythropoiesis, chronic hemolysis, and significant splenomegaly due to increased splenic sequestration and destruction of abnormal red blood cells. - **Splenectomy is often considered in thalassemia major** to reduce transfusion requirements and alleviate symptoms related to splenomegaly like abdominal discomfort and early satiety. *Congenital spherocytic anemia* - Also known as **hereditary spherocytosis**, this condition is caused by defects in red blood cell membrane proteins, leading to fragile, spherical red blood cells that are preferentially targeted and destroyed by the spleen [1]. - **Splenectomy is a highly effective treatment** for hereditary spherocytosis, as it removes the primary organ responsible for destroying the abnormal red blood cells, leading to a significant reduction in hemolysis and improvement in anemia [1].
Question 10: A 45-year-old male presents with fatigue, pale skin, and jaundice. Labs reveal hemolysis and a positive direct Coombs test. What is the most likely diagnosis?
- A. Hereditary spherocytosis
- B. Autoimmune hemolytic anemia (Correct Answer)
- C. Sickle cell anemia
- D. G6PD deficiency
Explanation: ***Autoimmune hemolytic anemia*** - The combination of **hemolysis** (fatigue, pale skin, jaundice) and a **positive direct Coombs test** is highly indicative of autoimmune hemolytic anemia [1]. - A positive direct Coombs test identifies **antibodies or complement components** bound to the surface of red blood cells, leading to their destruction [1]. *Hereditary spherocytosis* - This condition is characterized by **spherocytes** on a peripheral blood smear and an **increased osmotic fragility test** [3]. - While it causes hemolysis, a **direct Coombs test** would typically be negative as it's an intrinsic red blood cell defect, not antibody-mediated [1]. *Sickle cell anemia* - Characterized by **sickle-shaped red blood cells** and is diagnosed with **hemoglobin electrophoresis**. - While it causes hemolytic anemia, the direct Coombs test is typically **negative**, and symptoms often include **vaso-occlusive crises**. *G6PD deficiency* - This is an **X-linked recessive enzymopathy** leading to bite cells and **Heinz bodies** during oxidative stress [2]. - The direct Coombs test would be **negative**, as the hemolysis is due to enzyme deficiency, not antibodies [2].
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