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ABP Pediatric Hematology-Oncology study materials
ABP Pediatric Hematology-Oncology study resources

ABP Pediatric Hematology-Oncology practice questions

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Question 1Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

An otherwise healthy 2-month-old term infant born at 39 weeks has hemoglobin 9.4 g/dL, MCV 88 fL, and reticulocyte count 1.0%. Growth and feeding are normal. What is the most likely explanation?

  1. Physiologic anemia Correct answer.
  2. Beta-thalassemia major
  3. Hereditary spherocytosis
  4. Iron deficiency anemia

Explanation

Term infants normally reach a hemoglobin nadir of about 9 to 11 g/dL at 6 to 12 weeks as erythropoietin falls and red cell production transiently decreases. The low reticulocyte count and normal growth fit this physiologic nadir. It resolves without treatment as erythropoietin rises.

Question 2Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 15-month-old child drinks 1 L of cow milk daily and has hemoglobin 7.8 g/dL, MCV 68 fL, ferritin 6 ng/mL, and platelet count 450,000/µL. Which is the most appropriate next step?

  1. High-dose prednisone
  2. Hydroxyurea therapy
  3. Oral ferrous sulfate therapy Correct answer.
  4. Pack red blood cell transfusion

Explanation

Excessive cow milk intake causes iron deficiency, and the low ferritin with microcytic anemia is diagnostic. Oral ferrous sulfate is first-line therapy, along with dietary counseling to limit cow milk. Transfusion is reserved for severe symptomatic anemia or hemodynamic instability.

Question 3Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 5-year-old child from Southeast Asia has hemoglobin 11.8 g/dL, MCV 66 fL, normal ferritin, and normal hemoglobin electrophoresis. Which condition best explains these findings?

  1. Alpha-thalassemia trait Correct answer.
  2. Beta-thalassemia trait with elevated HbA2
  3. Iron deficiency anemia with low ferritin
  4. Lead poisoning with basophilic stippling

Explanation

Two-gene deletion alpha-thalassemia trait commonly causes microcytosis with mild or no anemia, normal ferritin, and normal hemoglobin electrophoresis. Beta-thalassemia trait usually raises HbA2, and iron deficiency lowers ferritin. Lead poisoning causes basophilic stippling and elevated blood lead.

Question 4Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 4-year-old boy develops jaundice and dark urine after eating fava beans. Blood smear shows bite cells and Heinz bodies. Deficiency of which enzyme is most likely?

  1. Pyruvate kinase
  2. G6PD Correct answer.
  3. Cytochrome b5 reductase
  4. Glutathione reductase

Explanation

G6PD deficiency causes episodic oxidative hemolysis after triggers such as fava beans, infection, or certain drugs. Heinz bodies and bite cells are characteristic. Cytochrome b5 reductase deficiency causes methemoglobinemia rather than this hemolytic picture.

Question 5Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 7-year-old has jaundice, splenomegaly, and gallstones. Blood shows spherocytes, MCHC 37 g/dL, and reticulocyte count 8%. Which diagnosis is most likely?

  1. Glucose-6-phosphate dehydrogenase deficiency
  2. Beta-thalassemia intermedia
  3. Hereditary spherocytosis Correct answer.
  4. Warm autoimmune hemolytic anemia

Explanation

Hereditary spherocytosis causes extravascular hemolysis, splenomegaly, pigment gallstones, and spherocytes with an elevated MCHC. The family history and chronic course are typical. G6PD deficiency causes episodic oxidative hemolysis without spherocytes.

Question 6Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 28-year-old Rh-negative mother gives birth to an Rh-positive infant. She has no anti-D antibodies. Which intervention best prevents Rh alloimmunization in this pregnancy?

  1. Give the mother Rh-positive red cells
  2. Give the infant anti-D immune globulin
  3. Give anti-D immune globulin Correct answer.
  4. Perform maternal splenectomy

Explanation

Anti-D immune globulin binds fetal Rh-positive red cells that enter the maternal circulation and prevents the mother from forming anti-D antibodies. It is given to Rh-negative unsensitized mothers during pregnancy and after delivery of an Rh-positive infant. Treating the infant or giving Rh-positive cells would not prevent maternal sensitization.

Question 7Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 10-month-old exclusively breastfed infant of a vegan mother has hemoglobin 8.2 g/dL, MCV 102 fL, hypersegmented neutrophils, normal folate, and low serum cobalamin. Which deficiency is most likely?

  1. Iron deficiency
  2. Vitamin B12 deficiency Correct answer.
  3. Folate deficiency
  4. Alpha-thalassemia trait

Explanation

Maternal vegan diet can lead to low vitamin B12 in breast milk, causing macrocytic anemia and hypersegmented neutrophils in the infant. Normal folate and low cobalamin confirm vitamin B12 deficiency. Iron deficiency causes microcytosis, and alpha-thalassemia trait causes microcytosis without hypersegmented neutrophils.

Question 8Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 6-month-old with sickle cell anemia (HbSS) is afebrile and up to date on vaccines. Which daily medication is recommended to reduce the risk of invasive pneumococcal disease?

  1. Trimethoprim-sulfamethoxazole
  2. Azithromycin
  3. Penicillin V Correct answer.
  4. Amoxicillin

Explanation

Daily penicillin V prophylaxis is recommended for young children with sickle cell anemia, generally starting by 2 months and continuing until at least 5 years of age. It reduces the risk of invasive pneumococcal infection, especially before full vaccine protection develops. Amoxicillin and azithromycin are not the standard daily prophylactic choice.

Question 9Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A child with iron deficiency anemia begins oral ferrous sulfate. At 1 week, which laboratory change is the earliest reliable sign of response?

  1. Normalization of serum ferritin
  2. Increase in mean corpuscular volume
  3. Fall in total iron-binding capacity
  4. Rise in reticulocyte count Correct answer.

Explanation

After starting iron, the reticulocyte count rises within about 3 to 7 days, before hemoglobin and red cell indices improve. Hemoglobin typically rises over 2 to 4 weeks, and ferritin normalizes later. MCV changes are delayed because circulating red cells have a long lifespan.

Question 10Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 12-year-old with juvenile idiopathic arthritis has hemoglobin 9.5 g/dL, MCV 76 fL, low serum iron, low total iron-binding capacity, and ferritin 220 ng/mL. Which diagnosis best fits?

  1. Anemia of inflammation Correct answer.
  2. Alpha-thalassemia trait
  3. Lead poisoning
  4. Iron deficiency anemia

Explanation

Chronic inflammation raises ferritin and lowers total iron-binding capacity while reducing available iron for erythropoiesis. This pattern distinguishes anemia of inflammation from iron deficiency, which usually has low ferritin and high total iron-binding capacity. The mild microcytosis is also consistent with inflammation.

Question 11Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 6-month-old of Mediterranean descent has severe pallor, hepatosplenomegaly, hemoglobin 4.5 g/dL, MCV 65 fL, and elevated HbF with absent HbA. Which diagnosis is most likely?

  1. Iron deficiency anemia
  2. Hereditary spherocytosis
  3. Transient erythroblastopenia of childhood
  4. Beta-thalassemia major Correct answer.

Explanation

Beta-thalassemia major presents at about 3 to 6 months as fetal hemoglobin declines, causing severe microcytic anemia, extramedullary hematopoiesis, and hepatosplenomegaly. Hemoglobin electrophoresis shows high HbF and little or no HbA. Transient erythroblastopenia causes isolated reticulocytopenia without this hemoglobin pattern.

Question 12Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 2-year-old with sickle cell anemia has sudden splenic enlargement, hemoglobin fall from 8.5 to 4.0 g/dL, and reticulocyte count 12%. Which management is most urgent?

  1. Start daily oral penicillin
  2. Observe closely in the outpatient clinic
  3. Transfuse red blood cells urgently Correct answer.
  4. Begin hydroxyurea therapy

Explanation

This is acute splenic sequestration, a life-threatening complication of sickle cell disease characterized by rapid splenic enlargement and falling hemoglobin. Urgent red cell transfusion restores intravascular volume and oxygen-carrying capacity. Observation, penicillin, and hydroxyurea do not treat the acute sequestration.

Question 13Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A child with hereditary spherocytosis develops fever, pallor, and hemoglobin 4 g/dL. Reticulocyte count is 0.2%, and the spleen is unchanged. Which complication is most likely?

  1. Folate deficiency
  2. Parvovirus aplastic crisis Correct answer.
  3. Splenic sequestration crisis
  4. Warm autoimmune hemolysis

Explanation

Parvovirus B19 temporarily suppresses erythropoiesis, causing a profound reticulocytopenia and rapid anemia in children with chronic hemolysis such as hereditary spherocytosis. The spleen is not acutely enlarged, which helps distinguish this from sequestration. Autoimmune hemolysis would usually show reticulocytosis and a positive direct antiglobulin test.

Question 14Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 3-year-old presents with cyanosis that does not improve with 100% oxygen. Arterial oxygen tension is normal, and blood is dark chocolate-colored. Which diagnosis is most likely?

  1. Sickle cell acute chest syndrome
  2. Methemoglobinemia Correct answer.
  3. Hereditary spherocytosis
  4. Glucose-6-phosphate dehydrogenase deficiency

Explanation

Methemoglobinemia causes cyanosis that is unresponsive to supplemental oxygen because oxidized iron cannot bind oxygen normally. Arterial oxygen tension may be normal, and the blood appears dark or chocolate-colored. Acute chest syndrome and hemolytic anemias do not produce this combination.

Question 15Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 4-year-old with pica and abdominal pain has hemoglobin 8.8 g/dL, MCV 70 fL, and basophilic stippling. Which test is most useful to confirm the suspected cause?

  1. Blood lead level Correct answer.
  2. Hemoglobin electrophoresis
  3. G6PD activity
  4. Serum ferritin

Explanation

Pica, abdominal pain, microcytic anemia, and basophilic stippling suggest lead poisoning. A blood lead level confirms the diagnosis and guides chelation decisions. Ferritin and hemoglobin electrophoresis evaluate other causes of microcytosis but do not confirm lead toxicity.

Question 16Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 3-month-old has pallor, hemoglobin 7.0 g/dL, MCV 96 fL, reticulocyte count 0.1%, normal platelet and white cell counts, and absent thumbs. Which diagnosis is most likely?

  1. Diamond-Blackfan anemia Correct answer.
  2. Transient erythroblastopenia of childhood
  3. Aplastic anemia
  4. Fanconi anemia

Explanation

Diamond-Blackfan anemia is a congenital pure red cell aplasia that presents in infancy with macrocytic anemia, reticulocytopenia, and normal platelet and white cell counts. Congenital anomalies such as thumb abnormalities may be present. Transient erythroblastopenia usually occurs in older toddlers without congenital anomalies.

Question 17Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 6-year-old with short stature, thumb anomalies, and café-au-lait spots develops pancytopenia. Which test is most specific for the suspected diagnosis?

  1. Serum ferritin and iron studies
  2. Hemoglobin electrophoresis
  3. Diepoxybutane breakage test Correct answer.
  4. Direct antiglobulin test

Explanation

Fanconi anemia causes congenital anomalies, progressive bone marrow failure, and hypersensitivity to DNA cross-linking agents. A chromosomal breakage study using diepoxybutane or mitomycin C is the specific diagnostic test. Iron studies, hemoglobin electrophoresis, and the direct antiglobulin test evaluate other hematologic disorders.

Question 18Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 5-year-old with chronic jaundice and anemia has no spherocytes, a negative direct antiglobulin test, and low red cell pyruvate kinase activity. Which finding is most consistent with this disorder?

  1. Acute chest syndrome
  2. Iron overload without transfusion
  3. Chronic hemolytic anemia Correct answer.
  4. Megaloblastic anemia

Explanation

Pyruvate kinase deficiency causes chronic extravascular hemolysis with jaundice, splenomegaly, and gallstones. It does not produce spherocytes or a positive direct antiglobulin test. Acute chest syndrome is a sickle cell complication, and megaloblastic anemia results from vitamin B12 or folate deficiency.

Question 19Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A child with beta-thalassemia major receives regular transfusions and has ferritin 3,000 ng/mL. Which oral iron chelator is appropriate?

  1. Deferasirox Correct answer.
  2. Penicillin V
  3. Hydroxyurea
  4. Deferoxamine

Explanation

Deferasirox is an oral iron chelator used to prevent transfusional iron overload in patients with beta-thalassemia major. Deferoxamine is also effective but requires parenteral administration. Penicillin and hydroxyurea do not remove excess iron.

Question 20Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A previously healthy 18-month-old develops mild pallor 2 weeks after a viral illness. Hemoglobin is 7.5 g/dL, reticulocyte count 0.2%, and platelet and white cell counts are normal. Recovery occurs spontaneously. Which diagnosis is most likely?

  1. Transient erythroblastopenia Correct answer.
  2. Parvovirus B19-induced aplastic crisis
  3. Diamond-Blackfan red cell aplasia
  4. Constitutional aplastic anemia

Explanation

Transient erythroblastopenia of childhood causes isolated reticulocytopenia and anemia after a viral illness in previously healthy toddlers, with normal platelets and white cells. It resolves spontaneously. Diamond-Blackfan anemia presents earlier and is persistent, while parvovirus aplastic crisis usually occurs in a child with underlying chronic hemolysis.

Question 21Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A child with sickle cell anemia presents with sudden hemiparesis and a new infarct on brain imaging. Which treatment is indicated urgently in addition to supportive care?

  1. Hydroxyurea therapy
  2. Aspirin therapy
  3. Exchange transfusion Correct answer.
  4. Simple red blood cell transfusion

Explanation

Acute stroke in sickle cell disease is treated with urgent exchange transfusion to lower the HbS percentage while avoiding a large rise in hematocrit and viscosity. Simple transfusion can raise viscosity and is not sufficient for acute stroke. Hydroxyurea and aspirin are not acute stroke treatments.

Question 22Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

Which alpha-globin genotype is most consistent with hemoglobin H disease?

  1. αα/αα
  2. --/αα
  3. --/-α Correct answer.
  4. -α/-α

Explanation

Hemoglobin H disease results from deletion of three of the four alpha-globin genes, leaving one functional gene. Excess beta-globin chains form beta-tetramers known as hemoglobin H. Two-gene deletion states cause alpha-thalassemia trait, not hemoglobin H disease.

Question 23Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 6-year-old develops dark urine and anemia after cold exposure. The direct antiglobulin test is positive only with complement, and the Donath-Landsteiner antibody is detected. Which diagnosis is most likely?

  1. Warm autoimmune hemolytic anemia
  2. Cold agglutinin disease
  3. Glucose-6-phosphate dehydrogenase deficiency
  4. Paroxysmal cold hemoglobinuria Correct answer.

Explanation

Paroxysmal cold hemoglobinuria is caused by a biphasic Donath-Landsteiner antibody that binds red cells in the cold and fixes complement, causing intravascular hemolysis on rewarming. The direct antiglobulin test is positive for complement only. Warm autoimmune hemolysis usually has IgG on the red cells, and G6PD deficiency is not antibody-mediated.

Question 24Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A young child has exocrine pancreatic insufficiency, neutropenia, and metaphyseal dysplasia. Which diagnosis is most likely?

  1. Fanconi anemia
  2. Severe congenital neutropenia
  3. Diamond-Blackfan anemia
  4. Shwachman-Diamond syndrome Correct answer.

Explanation

Shwachman-Diamond syndrome is a bone marrow failure disorder caused by SBDS mutations and characterized by exocrine pancreatic insufficiency, neutropenia, and skeletal abnormalities. Fanconi anemia causes pancytopenia with DNA breakage hypersensitivity, while Diamond-Blackfan anemia causes pure red cell aplasia.

Question 25Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A boy has microcytic anemia, ring sideroblasts on marrow examination, and a mutation in ALAS2. Which diagnosis is most likely?

  1. Iron deficiency anemia
  2. Lead poisoning
  3. Sideroblastic anemia Correct answer.
  4. Beta-thalassemia trait

Explanation

ALAS2 mutations cause X-linked congenital sideroblastic anemia, characterized by ring sideroblasts and ineffective erythropoiesis. Iron deficiency and beta-thalassemia trait do not produce ring sideroblasts. Lead poisoning can cause sideroblastic changes but is not caused by an ALAS2 mutation.

Question 26Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 10-week-old term infant has hemoglobin 9.8 g/dL, MCV 95 fL, reticulocyte count 1%, and normal platelet and white cell counts. Growth and feeding are normal. What is the most likely explanation?

  1. Diamond-Blackfan anemia
  2. Physiologic anemia Correct answer.
  3. Iron deficiency anemia
  4. Beta-thalassemia trait

Explanation

Term infants normally reach a hemoglobin nadir of about 9–11 g/dL at 6–12 weeks as erythropoietin falls after birth; the reticulocyte count is low and the MCV is normal. Iron deficiency is uncommon before 4–6 months in term infants and usually causes microcytosis. The findings are not severe enough for Diamond-Blackfan anemia, and thalassemia trait would produce microcytosis.

Question 27Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 2-day-old infant born to a group O mother is jaundiced. The infant is blood group A, the direct antiglobulin test is weakly positive, and the hemoglobin is 13 g/dL. Which diagnosis is most likely?

  1. G6PD deficiency
  2. ABO incompatibility Correct answer.
  3. Rh hemolytic disease
  4. Physiologic jaundice

Explanation

ABO incompatibility commonly affects infants of group O mothers with group A or B infants; the DAT may be weakly positive and anemia is often mild. Rh disease usually occurs in an Rh-negative mother with an Rh-positive infant and causes a strongly positive DAT. Physiologic jaundice appears after 24 hours but is not immune-mediated, and G6PD deficiency is not suggested by this presentation.

Question 28Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 4-year-old boy of Mediterranean descent develops dark urine and jaundice after eating fava beans. Hemoglobin is 7 g/dL, and the blood smear shows bite cells and Heinz bodies. Between episodes his hemoglobin is normal. Which diagnosis is most likely?

  1. Pyruvate kinase deficiency
  2. G6PD deficiency Correct answer.
  3. Warm autoimmune hemolytic anemia
  4. Hereditary spherocytosis

Explanation

G6PD deficiency causes episodic oxidative hemolysis after fava beans, infection, or oxidant drugs; bite cells and Heinz bodies are characteristic, and hemoglobin is normal between episodes. Pyruvate kinase deficiency causes chronic hemolysis, and hereditary spherocytosis causes spherocytes with chronic or intermittent anemia. Warm autoimmune hemolytic anemia would have a positive direct antiglobulin test and no Heinz bodies.

Question 29Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 12-year-old boy is found to have sickle cell trait. Which complication is associated with this condition?

  1. Chronic hemolytic anemia
  2. Acute chest syndrome
  3. Splenic sequestration crisis
  4. Painless hematuria Correct answer.

Explanation

Sickle cell trait is usually asymptomatic but can cause painless hematuria from renal medullary microinfarction or papillary necrosis. Chronic hemolysis, splenic sequestration, and acute chest syndrome are features of sickle cell disease, not trait. Counseling should include awareness of rare complications such as hematuria and exercise-related rhabdomyolysis.

Question 30Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 9-year-old with sickle cell anemia has fever, cough, chest pain, and a new pulmonary infiltrate. Oxygen saturation is 88% on room air. Which initial management is most appropriate?

  1. Antibiotics, oxygen, and transfusion Correct answer.
  2. Oral amoxicillin with outpatient follow-up
  3. Hydroxyurea at a higher dose
  4. Incentive spirometry alone

Explanation

Acute chest syndrome is a leading cause of death in sickle cell disease and requires prompt broad-spectrum antibiotics, oxygen, hydration, analgesia, and transfusion for hypoxia or worsening anemia. Simple transfusion is often adequate; exchange transfusion is used for severe or worsening disease. Outpatient therapy or spirometry alone is inadequate for a hypoxic child.

Question 31Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 5-year-old from Southeast Asia has hemoglobin 10.5 g/dL, MCV 65 fL, RBC count 5.8 million/µL, normal iron studies, and elevated hemoglobin A2. Which diagnosis is most likely?

  1. Anemia of chronic inflammation
  2. Alpha-thalassemia trait
  3. Beta-thalassemia trait Correct answer.
  4. Iron deficiency anemia

Explanation

Elevated hemoglobin A2 with microcytosis and normal iron studies supports beta-thalassemia trait. The high RBC count and low MCV (Mentzer index below 13) also favor thalassemia over iron deficiency. Alpha-thalassemia trait does not raise hemoglobin A2.

Question 32Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 7-year-old has pallor, jaundice, hemoglobin 6.8 g/dL, reticulocyte count 12%, and spherocytes. The direct antiglobulin test is positive with anti-IgG only. Which initial therapy is most appropriate?

  1. Oral corticosteroids Correct answer.
  2. Intravenous immunoglobulin
  3. Therapeutic plasma exchange
  4. Splenectomy

Explanation

This is warm autoimmune hemolytic anemia, for which corticosteroids are first-line therapy. Transfusion may be needed for severe symptomatic anemia, but IVIG and plasma exchange are not standard initial treatments. Splenectomy is reserved for refractory disease because of infection risk.

Question 33Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 6-year-old has splenomegaly, jaundice, and anemia with spherocytes on smear. The direct antiglobulin test is negative, and the family history is positive. Which test is most confirmatory for hereditary spherocytosis?

  1. EMA binding test Correct answer.
  2. Hemoglobin electrophoresis
  3. Serum haptoglobin
  4. Bone marrow aspirate

Explanation

The eosin-5-maleimide (EMA) binding test detects reduced band 3 on red cells and is a sensitive confirmatory test for hereditary spherocytosis. Osmotic fragility testing is an alternative, while bone marrow examination and hemoglobin electrophoresis do not diagnose the disorder. Haptoglobin is usually low in hemolysis but is nonspecific.

Question 34Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 10-year-old has severe acquired aplastic anemia with no matched sibling donor and no active infection. Which initial therapy is most appropriate?

  1. ATG plus cyclosporine Correct answer.
  2. Splenectomy
  3. Oral prednisone as monotherapy
  4. Hydroxyurea

Explanation

For acquired severe aplastic anemia without a matched sibling donor, immunosuppressive therapy with horse antithymocyte globulin plus cyclosporine is standard first-line treatment. Matched sibling hematopoietic cell transplantation is preferred when a suitable donor exists. Corticosteroids alone, splenectomy, and hydroxyurea are not effective definitive therapies.

Question 35Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A child with thalassemia major has received chronic transfusions for years, and serum ferritin is 2,500 ng/mL. Which test best estimates myocardial iron overload?

  1. Serum ferritin measurement
  2. Echocardiography
  3. Liver biopsy
  4. Cardiac T2* MRI Correct answer.

Explanation

Cardiac T2* MRI noninvasively estimates myocardial iron deposition and is the preferred test for guiding chelation therapy. Serum ferritin is useful for trends but correlates poorly with cardiac iron. Liver biopsy assesses hepatic iron but does not directly measure myocardial iron, and echocardiography detects functional consequences rather than iron load.

Question 36Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A term newborn is pale and tachycardic at 6 hours of life. Hemoglobin is 6 g/dL, reticulocyte count is 0.5%, and bilirubin is normal. The mother's Kleihauer-Betke test shows increased fetal cells. Which diagnosis is most likely?

  1. Fetomaternal hemorrhage Correct answer.
  2. G6PD deficiency
  3. Physiologic anemia of infancy
  4. ABO incompatibility

Explanation

Fetomaternal hemorrhage causes acute blood loss with early pallor, tachycardia, low hemoglobin, and a low reticulocyte count because the marrow has not had time to respond. A positive Kleihauer-Betke test supports the diagnosis. ABO incompatibility and G6PD deficiency cause hemolysis with jaundice and reticulocytosis, and physiologic anemia occurs later with a low reticulocyte count but not this degree of anemia at 6 hours.

Question 37Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 2-year-old with sickle cell anemia presents with a temperature of 39.5°C and no focal findings. Which is the most appropriate next step?

  1. Cultures and parenteral antibiotics Correct answer.
  2. Acetaminophen alone
  3. Wait for culture results before antibiotics
  4. Oral amoxicillin and home observation

Explanation

Children with sickle cell disease are functionally asplenic and at high risk for overwhelming bacterial sepsis, so fever requires immediate blood cultures and empiric parenteral antibiotics. Outpatient oral therapy or observation is unsafe. Acetaminophen treats fever but does not address the infection risk.

Question 38Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 12-year-old has episodic dark urine, fatigue, and pancytopenia. Lactate dehydrogenase is elevated, and flow cytometry shows loss of CD55 and CD59 on red cells. Which diagnosis is most likely?

  1. Warm autoimmune hemolytic anemia
  2. PNH Correct answer.
  3. G6PD deficiency
  4. Hereditary spherocytosis

Explanation

Loss of CD55 and CD59, complement-regulatory proteins, is diagnostic of paroxysmal nocturnal hemoglobinuria (PNH), which causes complement-mediated intravascular hemolysis and can lead to pancytopenia. Warm autoimmune hemolytic anemia would be DAT-positive and does not lack these markers. G6PD deficiency and hereditary spherocytosis do not produce the CD55/CD59 defect.

Question 39Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 7-year-old boy has nail dystrophy, oral leukoplakia, reticulated skin hyperpigmentation, and progressive pancytopenia. A paternal uncle died of pulmonary fibrosis. Which diagnosis is most likely?

  1. Shwachman-Diamond syndrome
  2. Diamond-Blackfan anemia
  3. Fanconi anemia
  4. Dyskeratosis congenita Correct answer.

Explanation

The triad of nail dystrophy, oral leukoplakia, and reticulated hyperpigmentation with bone marrow failure is characteristic of dyskeratosis congenita, a telomere biology disorder that can include pulmonary fibrosis in relatives. Fanconi anemia typically has skeletal and renal anomalies and increased chromosomal breakage. Shwachman-Diamond causes pancreatic insufficiency and neutropenia, and Diamond-Blackfan anemia causes isolated red cell aplasia.

Question 40Hematology (red cell disorders, anemias, hemoglobinopathies, and bone marrow failure)

A 15-year-old with sickle cell anemia has a painful erection lasting 5 hours despite hydration and analgesia. Which is the most appropriate next step?

  1. Oral hydroxyurea
  2. Immediate splenectomy
  3. Continue observation with analgesia
  4. Corporal aspiration and irrigation Correct answer.

Explanation

Priapism lasting more than 4 hours is an emergency and requires urologic intervention such as aspiration and irrigation of the corpora cavernosa, often with intracavernosal alpha-agonist therapy. Prolonged observation risks ischemia and permanent erectile dysfunction. Hydroxyurea may reduce recurrent priapism but does not treat an acute episode, and splenectomy has no role.

Question 41Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

A newborn receives intramuscular vitamin K shortly after birth primarily to prevent which complication?

  1. Hemophilia A from factor VIII deficiency
  2. Heparin-induced thrombocytopenia
  3. Vitamin K deficiency bleeding Correct answer.
  4. Neonatal alloimmune thrombocytopenia

Explanation

Newborns have limited vitamin K stores and sterile gut flora, so they are at risk of vitamin K deficiency bleeding in the first weeks to months of life. Intramuscular vitamin K at birth prevents both classic and late vitamin K deficiency bleeding. The other listed disorders are caused by immune, genetic, or drug-related mechanisms and are not prevented by vitamin K.

Question 42Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

A 4-year-old previously healthy child has sudden petechiae and bruising, a platelet count of 12,000/µL, normal hemoglobin, normal white cell count, and no organomegaly. What is the most likely diagnosis?

  1. Acute lymphoblastic leukemia
  2. Hemophilia A
  3. Disseminated intravascular coagulation
  4. Immune thrombocytopenia Correct answer.

Explanation

Sudden isolated thrombocytopenia with mucocutaneous bleeding in an otherwise well child is typical of immune thrombocytopenia. Leukemia more often produces additional cytopenias, blasts, or organomegaly; hemophilia causes deep bleeding with a normal platelet count; DIC produces abnormal coagulation tests and a consumptive picture.

Question 43Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

Hemophilia A is inherited in which pattern?

  1. Autosomal recessive
  2. Autosomal dominant
  3. X-linked recessive Correct answer.
  4. Mitochondrial

Explanation

Hemophilia A results from a deficiency of factor VIII encoded by the F8 gene on the X chromosome. It therefore affects males predominantly, while female carriers may have variable factor levels. Autosomal and mitochondrial patterns do not apply.

Question 44Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

Which inherited bleeding disorder is the most common in children?

  1. Severe factor XIII deficiency
  2. Hemophilia B
  3. von Willebrand disease Correct answer.
  4. Hemophilia A

Explanation

von Willebrand disease is the most common inherited bleeding disorder, affecting both sexes and often causing mucocutaneous bleeding. Hemophilia A and B are less common and cause deep bleeding. Factor XIII deficiency is rare.

Question 45Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

Which agent is used to reverse unfractionated heparin?

  1. Vitamin K
  2. Fresh frozen plasma
  3. Protamine sulfate Correct answer.
  4. Idarucizumab

Explanation

Protamine sulfate binds heparin and neutralizes its anticoagulant effect. Vitamin K reverses warfarin, and idarucizumab reverses dabigatran. Fresh frozen plasma replaces clotting factors but is not a direct heparin antidote.

Question 46Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

Which laboratory test is used to monitor warfarin therapy?

  1. Thrombin time
  2. Bleeding time
  3. Activated partial thromboplastin time
  4. International normalized ratio Correct answer.

Explanation

Warfarin reduces the vitamin K-dependent factors II, VII, IX, and X, and its effect is monitored with the prothrombin time expressed as the international normalized ratio. The aPTT is used mainly to monitor unfractionated heparin. Bleeding time and thrombin time do not reflect warfarin effect.

Question 47Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

A child taking aspirin may have prolonged bleeding because aspirin does what?

  1. Reduces von Willebrand factor synthesis
  2. Activates antithrombin
  3. Depletes factor VIII
  4. Blocks platelet cyclooxygenase Correct answer.

Explanation

Aspirin irreversibly acetylates platelet cyclooxygenase-1, reducing thromboxane A2 production and platelet aggregation for the lifespan of the platelet. This can prolong the bleeding time even when the platelet count is normal. It does not reduce VWF, deplete factor VIII, or activate antithrombin.

Question 48Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

Which bleeding pattern is most characteristic of hemophilia?

  1. Deep joint and muscle bleeding Correct answer.
  2. Immediate bleeding after superficial cuts
  3. Thrombocytopenia with bruising
  4. Petechiae and mucosal oozing

Explanation

Hemophilia causes deficiency of factor VIII or IX and leads to delayed, deep bleeding into joints and muscles. Platelet disorders more often cause immediate mucocutaneous bleeding and petechiae. The platelet count is normal in hemophilia.

Question 49Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

A child with newly diagnosed immune thrombocytopenia has a platelet count of 18,000/µL and only mild bruising. What is the most appropriate initial management?

  1. Intravenous heparin
  2. Immediate splenectomy
  3. Prophylactic platelet transfusion to keep the count above 50,000/µL
  4. Observation without platelet transfusion Correct answer.

Explanation

Management of pediatric immune thrombocytopenia is guided by bleeding severity rather than the platelet count alone. A child with mild bruising can often be observed, because platelet transfusions are usually ineffective and are reserved for life-threatening bleeding. Splenectomy is not initial therapy, and heparin would increase bleeding risk.

Question 50Hemostasis and Thrombosis (coagulation disorders, platelet disorders, and antithrombotic therapy)

A boy with severe hemophilia A has recurrent hemarthroses. Which strategy best prevents joint damage?

  1. On-demand factor VIII only after each bleed
  2. Daily aspirin to prevent thrombosis
  3. Platelet transfusions before sports
  4. Regular prophylactic factor VIII infusions Correct answer.

Explanation

Regular prophylactic factor VIII infusions maintain trough levels and reduce spontaneous joint bleeding, which prevents chronic arthropathy in severe hemophilia. On-demand therapy treats bleeding after it starts but is less effective for joint protection. Aspirin and platelet transfusions are not appropriate.