Hematology

Question 1

An 8-year-old boy is brought to the pediatrician after his parents noticed very dark urine in the toilet earlier that morning. Initial laboratory studies show intravascular hemolysis; further testing shows that his RBCs are susceptible to complement-mediated lysis. This patient most likely has which of the following conditions?
(A) Autoimmune hemolytic anemia
(B) Common bile duct stricture
(C) Hereditary spherocytosis
(D) Paroxysmal nocturnal hemoglobinuria
(E) Thrombotic thrombocytopenic purpura

Answer 1

(D) Paroxysmal nocturnal hemoglobinuria

Question 2

A 3-year-old girl was in her usual state of good health 1 month ago when she developed an acute viral upper respiratory infection. She now presents to the emergency department with nonbranching purple skin lesions. The rest of her physical examination is unremarkable. The complete blood count demonstrates a low platelet count, while the peripheral blood smear is notable only for large platelets. Which of the following laboratory findings would most likely be present in this patient?
(A) Antiplatelet antibodies
(B) Decreased megakaryocytes on bone marrow biopsy
(C) IgA deficiency
(D) Increased fibrin split products
(E) Vitamin K deficiency

Answer 2

(A) Antiplatelet antibodies

Question 3

A 16-year-old boy is brought to the emergency department because of the acute onset of fever, chills, and a productive cough. X-ray of the chest shows an infiltrate restricted to the left lower lobe. Samples taken of the sputum show α-hemolytic gram-positive cocci in pairs. The patient says that he has had similar infections over the past year. A peripheral blood smear is done, and results show several sickle-shaped RBCs. Which of the following explains why this patient is susceptible to this infection?
(A) Bone marrow infiltration resulting in neutropenia and compromised immune function
(B) Large vessel occlusions in the cerebral vasculature resulting in neurologic events and
aspiration pneumonia
(C) Microvascular infarcts resulting in pulmonary failure
(D) Microvascular infarcts resulting in splenic dysfunction
(E) Vaso-occlusion in the renal medulla

Answer 3

(D) Microvascular infarcts resulting in splenic dysfunction

Question 4

A child is brought to the pediatrician because her parents are concerned about lead poisoning since their house is known to contain lead-based paint. A complete blood cell count reveals anemia. Lead poisoning causes anemia because it does which of the following?
(A) Disrupts heme synthesis by causing decreased iron absorption from the gut
(B) Disrupts heme synthesis by increasing the activity of aminolevulinate dehydratase
(C) Disrupts heme synthesis by inhibiting ferrochelatase
(D) Disrupts hemoglobin function by binding to hemoglobin with high affinity, preventing oxygen binding
(E) Disrupts RBC DNA synthesis, causing megaloblastic changes in RBCs

Answer 4

(C) Disrupts heme synthesis by inhibiting ferrochelatase