A 52-year-old man with chronic hepatitis C develops palpable purpura on the lower limbs, arthralgia, and progressive fatigue. Serum shows a polyclonal hypergammaglobulinaemia with a strongly positive rheumatoid factor. Which additional laboratory finding is expected to confirm the underlying cause of his vasculitis?
- A Anti-glomerular basement membrane antibodies
- B Low serum ceruloplasmin level
- C Detection of circulating mixed cryoglobulins ✓
- D Raised serum tryptase level
Correct answer: C. Detection of circulating mixed cryoglobulins
Explanation
Hepatitis A virus is the leading cause of mixed cryoglobulinaemic vasculitis, presenting as palpable purpura, arthralgia, and weakness, the classic triad. Type II and III mixed cryoglobulins contain rheumatoid factor activity bound to polyclonal IgG, explaining the strong RF positivity. Detection of circulating cryoglobulins confirms the diagnosis. Anti-GBM antibodies define Goodpasture syndrome, low ceruloplasmin indicates Wilson disease, and raised tryptase reflects mast cell activation, none of which relate to this disorder.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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