MLT GlobeHematology: Hemolytic anemias & hemoglobinopathies – page 2
120 Hematology MCQs on Hemolytic anemias & hemoglobinopathies with answers and explanations.
Hydroxyurea reduces painful crises in sickle cell disease mainly by:
Hydroxyurea raises HbF, which does not enter HbS polymers and so reduces sickling. It does not change the beta-globin mutation, so HbS is not converted to HbA.
Hb Bart's hydrops fetalis results from which alpha-globin genotype?
With no functional alpha genes, the fetus makes only gamma-4 tetramers (Hb Bart's), which cannot deliver oxygen, leading to hydrops. The --/-α genotype causes HbH disease, which is compatible with life.
HbH disease results from deletion or inactivation of how many of the four alpha-globin genes?
HbH disease (--/-α) has only one working alpha gene, so excess beta chains form HbH (β4). Two deletions give alpha-thalassemia trait; four deletions cause Hb Bart's hydrops fetalis.
A healthy adult is found to have a single alpha-globin gene deletion (-α/αα). Which laboratory picture is most typical?
A silent carrier has three working alpha genes, so the blood count is usually normal or shows only slight microcytosis. HbH inclusions need three deleted genes, and raised HbA2 points to beta-thalassemia trait.
Children with sickle cell anemia are given penicillin prophylaxis mainly because functional asplenia greatly raises the risk of sepsis from:
Repeated splenic infarction causes loss of splenic function, and the spleen is key for clearing encapsulated bacteria such as S. pneumoniae. The other organisms are not linked specifically to asplenia.
Which condition promotes HbS polymerization and red cell sickling?
Deoxygenation, acidosis, dehydration and cold favor HbS polymerization. HbF does not join the polymer, and alpha-thalassemia lowers MCHC, so both reduce sickling.
Both parents have beta-thalassemia trait. What is the chance that each pregnancy will result in a child with beta-thalassemia major?
Beta-thalassemia is autosomal recessive. Two carriers have a 1 in 4 chance of an affected child, 1 in 2 of a carrier and 1 in 4 of an unaffected non-carrier child.
A transfusion-dependent patient with beta-thalassemia major is receiving iron chelation. Which laboratory test is most commonly used for routine monitoring of iron load?
Regular transfusion causes iron overload, and serum ferritin is the usual serial test to guide chelation (with MRI for organ iron). Haptoglobin reflects hemolysis, not iron stores.
A young adult with hereditary spherocytosis has recurrent right upper abdominal pain after meals. The most likely related complication is:
Chronic extravascular hemolysis raises bilirubin excretion into bile, forming pigment gallstones, which are common in hereditary spherocytosis. Portal thrombosis is linked with PNH, not HS.
Hemolytic anemia is anemia caused by:
In hemolytic anemia, red cells are destroyed before their normal 120-day lifespan, and the marrow cannot keep up.
In hemolytic anemia, which bilirubin fraction is mainly raised in serum?
Increased heme breakdown produces more unconjugated bilirubin than the liver can conjugate. Conjugated bilirubin rises mainly in liver or biliary disease.
Hemoglobin C results from replacing glutamic acid at position 6 of the beta chain with:
HbC has lysine at beta-6, while HbS has valine at the same position.
Hemoglobin E is most common in people from:
HbE is very common in Southeast Asia (for example Thailand, Cambodia and Laos) and nearby regions. HbC and HbS are more common in West Africa.
Which drug is an iron chelator used in transfusion-dependent thalassemia?
Deferoxamine (and oral agents such as deferasirox) binds excess iron so it can be excreted, preventing damage from transfusional iron overload.
The most common type of crisis in sickle cell disease is:
Painful vaso-occlusive crises, caused by sickled cells blocking small vessels, are by far the most common. The other crises are less frequent but can be severe.
Compared with adult HbA, fetal hemoglobin (HbF) has:
HbF (α2γ2) binds 2,3-BPG poorly, so it holds oxygen more tightly. This helps the fetus take oxygen from maternal blood.
Sickle cell trait gives partial protection against:
People with HbAS are partly protected from severe falciparum malaria, which explains the high frequency of the HbS gene in malarial regions.
When old red cells are broken down in macrophages, the heme (after iron is removed) is converted to:
Heme oxygenase opens the heme ring to form biliverdin, which is reduced to unconjugated bilirubin. The iron is recycled.
Cold autoimmune hemolytic anemia is usually caused by an autoantibody of which class?
Cold agglutinins are usually IgM, which bind red cells in the cold and activate complement. Warm AIHA is usually IgG.
Increased activity of the hexose monophosphate shunt in red cells mainly provides which products?
The shunt makes NADPH, which keeps glutathione reduced to protect hemoglobin and membranes from oxidants. G6PD deficiency blocks this step. ATP and 2,3-BPG come from glycolysis.