Clinical scenario: anemia | blood transfusion | splenomegaly
An 8-year-old boy has a history of intermittent jaundice since infancy and recurrent episodes of anemia requiring occasional blood transfusions. His father underwent splenectomy during childhood for a chronic hemolytic anemia.
He now presents with a 3-day history of lethargy and pallor following a mild febrile illness. There is no bleeding.
On examination:
- Temperature: 37.5°C
- Marked pallor
- Mild scleral icterus
- Spleen palpable 3 cm below the left costal margin
Investigations:
- Hemoglobin: 4.8 g/dL (baseline 10.2 g/dL)
- MCV: 88 fL
- Reticulocyte count: 0.3%
- Total bilirubin: 2.1 mg/dL
- Direct Coombs test: Negative
- Peripheral blood smear: Numerous spherocytes
What is the most likely cause of this acute deterioration?
A. Autoimmune hemolytic anemia
B. Acute splenic sequestration crisis
C. Parvovirus B19 infection causing aplastic crisis
D. Glucose-6-phosphate dehydrogenase deficiency
E. Hemolytic transfusion reaction
Correct answer & Explanation:
Correct Answer: C. Parvovirus B19 infection causing aplastic crisis
Explanation
This child has hereditary spherocytosis (HS), suggested by:
- Family history of hemolytic anemia/splenectomy
- Chronic jaundice
- Splenomegaly
- Spherocytes on peripheral smear
- Negative direct Coombs test
The acute fall in hemoglobin associated with a markedly low reticulocyte count is diagnostic of an aplastic crisis, most commonly caused by parvovirus B19.
Patients with chronic hemolytic anemia depend on increased erythropoiesis. Temporary suppression of the bone marrow by parvovirus B19 can result in profound anemia.
Why the other options are incorrect
A. Autoimmune hemolytic anemia
- Usually has a positive direct Coombs test.
B. Acute splenic sequestration crisis
- Characteristic of sickle cell disease and presents with sudden splenic enlargement and reticulocytosis.
C. Parvovirus B19 infection causing aplastic crisis ✅
- Correct. The hallmark is severe anemia with reticulocytopenia.
D. Glucose-6-phosphate dehydrogenase deficiency
- Produces episodic hemolysis with reticulocytosis, bite cells, and Heinz bodies rather than spherocytes.
E. Hemolytic transfusion reaction
- Requires a recent blood transfusion and is associated with evidence of acute hemolysis rather than marrow suppression.
High-yield pearl
Hereditary spherocytosis + sudden severe anemia + reticulocytopenia = Parvovirus B19 aplastic crisis until proven otherwise.
A common examination trap is confusing aplastic crisis with hemolytic crisis:
- Aplastic crisis: Low reticulocyte count
- Hemolytic crisis: High reticulocyte count
This distinction is frequently tested in postgraduate pediatric and hematology examinations.
