Virology: parvovirus B19: practice question

A Microbiology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Microbiology · Virology: parvovirus B19

Sample item

A 10-year-old with sickle cell disease has sudden pallor and fatigue. Haemoglobin has fallen to 4 g/dL and the reticulocyte count is nearly zero. What is the mechanism?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Parvovirus B19 infection of erythroid progenitors via the P antigen

Parvovirus B19 is a small single-stranded DNA virus that binds the P antigen (globoside) on erythroid progenitors and halts red cell production. In people with shortened red cell survival, as in sickle cell disease, this causes a transient aplastic crisis with reticulocytopenia. In healthy children it causes erythema infectiosum.

Option by option

  • A. Hyperhaemolysis from a G6PD deficiency

    G6PD haemolysis would increase reticulocytes rather than suppress them.

  • B. Splenic sequestration of red cells

    Sequestration produces a raised reticulocyte count and a big spleen.

  • C. Parvovirus B19 infection of erythroid progenitors via the P antigen (correct)

    Correct. Infection of erythroid precursors causes arrest of red cell production.

  • D. Autoimmune haemolysis from cold agglutinins

    Cold agglutinin haemolysis is associated with Mycoplasma and also gives reticulocytosis.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is C, Parvovirus B19 infection of erythroid progenitors via the P antigen. Parvovirus B19 is a small single-stranded DNA virus that binds the P antigen (globoside) on erythroid progenitors and halts red cell production.

Why is "Hyperhaemolysis from a G6PD deficiency" not the answer?

G6PD haemolysis would increase reticulocytes rather than suppress them.

Why is "Splenic sequestration of red cells" not the answer?

Sequestration produces a raised reticulocyte count and a big spleen.

Why is "Autoimmune haemolysis from cold agglutinins" not the answer?

Cold agglutinin haemolysis is associated with Mycoplasma and also gives reticulocytosis.

What concept does this question test?

It tests Virology: parvovirus B19 in Microbiology. In people with shortened red cell survival, as in sickle cell disease, this causes a transient aplastic crisis with reticulocytopenia. In healthy children it causes erythema infectiosum.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Virology: parvovirus B19?

Make a one-line identity card for each organism: shape and stain, defining test, toxin, disease and drug. Then use the flashcards and the other Microbiology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.