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Dermatology · Leprosy: secondary amyloidosis
Sample itemA man with lepromatous leprosy of 20 years and repeated ENL has oedema and heavy proteinuria. Renal biopsy shows amorphous deposits that stain with Congo red, and the apple-green birefringence is lost after potassium permanganate treatment. Which protein is deposited?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
C. Serum amyloid A
Chronic inflammation in lepromatous leprosy can lead to reactive systemic AA amyloidosis, a recognised cause of renal failure in neglected cases. AA amyloid is the permanganate-sensitive type, while AL amyloid is permanganate-resistant.
Option by option
A. Immunoglobulin light chain
AL amyloid arises from plasma cell dyscrasias and resists permanganate.
B. Beta-2 microglobulin
Beta-2 microglobulin amyloid occurs in long-term dialysis.
C. Serum amyloid A (correct)
Correct. Serum amyloid A derived deposits fit chronic inflammation and permanganate sensitivity.
D. Transthyretin
Transthyretin amyloid is hereditary or senile and also resists permanganate.
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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