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AL Amyloidosis — RACP Adult Medicine MCQ

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ModerateNephrologyAL AmyloidosisRACP Adult Medicine

A 68-year-old man presents with progressive bilateral leg oedema, proteinuria (8 g/day), and hypoalbuminaemia. He has a known IgG lambda paraprotein of 12 g/L. Renal biopsy with Congo red staining shows apple-green birefringence under polarised light. What is the diagnosis?

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Correct answer: B — AL amyloidosis

Congo red staining with apple-green birefringence under polarised light is the hallmark of amyloidosis. In the context of an IgG lambda paraprotein, this is AL (light chain) amyloidosis. Amyloid fibrils are derived from misfolded immunoglobulin light chains. Typing (mass spectrometry or immunohistochemistry) is essential to distinguish AL from AA amyloidosis. Treatment targets the underlying clonal plasma cell disorder.

Reference: eTG – 2025 – Haematology; BSH – 2021 – AL Amyloidosis Guidelines