A 48-year-old woman with chronic hepatitis C presents with episodic palpable purpura over the lower limbs, arthralgia, and weakness. Rheumatoid factor is weakly positive, serum C4 is markedly low, and skin biopsy shows leucocytoclastic vasculitis. What is the most likely mechanism of her condition?
- A Deposition of immune complexes containing HCV antigens and monoclonal IgM with polyclonal IgG ✓
- B Direct cytopathic effect of HCV on dermal endothelial cells
- C Anti-neutrophil cytoplasmic antibody mediated small vessel necrotising vasculitis
- D Type IV hypersensitivity reaction to antiviral drugs
Correct answer: A. Deposition of immune complexes containing HCV antigens and monoclonal IgM with polyclonal IgG
Explanation
Mixed cryoglobulinaemia is the best described extrahepatic manifestation of chronic hepatitis C. B cell expansion driven by the virus leads to cryoprecipitable immune complexes of HCV antigen, rheumatoid factor positive IgM, and polyclonal IgG that deposit in small vessels, consuming complement and lowering C4. The classic triad of palpable purpura, arthralgia, and weakness reflects this complex deposition, not direct viral cytopathy or ANCA mediated injury.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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