Immunology: mixed cryoglobulinaemia: 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 · Immunology: mixed cryoglobulinaemia

Sample item

A 55-year-old man with chronic hepatitis C has palpable purpura, arthralgia and glomerulonephritis. A blood sample kept at 4 degrees C develops a precipitate that redissolves on warming, and complement C4 is low. What is the precipitate?

AFibrinogen degradation productsBMonoclonal IgM rheumatoid factor bound to polyclonal IgGCIgE bound to viral antigenDMonoclonal IgG paraprotein alone

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

The answer and the reasoning

B. Monoclonal IgM rheumatoid factor bound to polyclonal IgG

In type II mixed cryoglobulinaemia, a monoclonal IgM with rheumatoid factor activity binds the Fc of polyclonal IgG, forming immune complexes that precipitate in the cold and deposit in small vessels. This type III hypersensitivity is strongly associated with hepatitis C and consumes complement, especially C4. Treatment includes antiviral therapy.

Option by option

A. Fibrinogen degradation products
Fibrinogen degradation products do not cause a cold-reversible precipitate in this setting.
B. Monoclonal IgM rheumatoid factor bound to polyclonal IgG (correct)
Correct. IgM rheumatoid factor complexed with IgG forms cold-precipitable immune complexes.
C. IgE bound to viral antigen
IgE is not part of cryoglobulins and mediates immediate hypersensitivity.
D. Monoclonal IgG paraprotein alone
A monoclonal IgG alone is the pattern of type I cryoglobulinaemia, which typically causes hyperviscosity and is seen in plasma cell disorders.

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.

Questions about this Microbiology question

What is the answer to this Microbiology question?

The best answer is B, Monoclonal IgM rheumatoid factor bound to polyclonal IgG. In type II mixed cryoglobulinaemia, a monoclonal IgM with rheumatoid factor activity binds the Fc of polyclonal IgG, forming immune complexes that precipitate in the cold and deposit in small vessels.

Why is "Fibrinogen degradation products" not the answer?

Fibrinogen degradation products do not cause a cold-reversible precipitate in this setting.

Why is "IgE bound to viral antigen" not the answer?

IgE is not part of cryoglobulins and mediates immediate hypersensitivity.

Why is "Monoclonal IgG paraprotein alone" not the answer?

A monoclonal IgG alone is the pattern of type I cryoglobulinaemia, which typically causes hyperviscosity and is seen in plasma cell disorders.

What concept does this question test?

It tests Immunology: mixed cryoglobulinaemia in Microbiology. This type III hypersensitivity is strongly associated with hepatitis C and consumes complement, especially C4. Treatment includes antiviral therapy.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Immunology: mixed cryoglobulinaemia?

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.