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AL Amyloidosis — SCE Rheumatology MCQ

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HardConnective Tissue DiseaseAL AmyloidosisSCE Rheumatology

A 50-year-old man with an 18-year history of seropositive erosive rheumatoid arthritis develops bilateral carpal tunnel syndrome. Examination shows macroglossia, periorbital purpura and peripheral oedema. His urine albumin:creatinine ratio is 420 mg/mmol and serum albumin is 22 g/L. Serum immunofixation detects an IgG-lambda monoclonal protein, with a serum free light-chain ratio of 0.05. Haemoglobin and adjusted calcium are normal, and whole-body low-dose CT shows no lytic lesions. Which diagnosis best unifies these findings?

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Correct answer: C — Systemic AL amyloidosis

Systemic AL amyloidosis is the best unifying diagnosis. Nephrotic-range albuminuria, bilateral carpal tunnel syndrome, macroglossia and periorbital purpura constitute a characteristic multisystem amyloid phenotype; the monoclonal IgG-lambda protein and markedly suppressed free light-chain ratio identify a likely lambda-producing plasma-cell clone. AA amyloidosis is a genuine concern in longstanding RA and commonly affects the kidneys, but macroglossia and periorbital purpura strongly favour AL disease. ATTR amyloidosis can cause carpal tunnel syndrome but does not explain the monoclonal light-chain findings and rarely causes this soft-tissue phenotype. Multiple myeloma can coexist with AL amyloidosis, but myeloma without amyloid does not unify the macroglossia and purpura. Confirmation requires Congo-red-positive tissue followed by definitive amyloid fibril typing; a monoclonal protein alone does not prove that deposits are AL.

Reference: Palladini G, Milani P, Merlini G. Management of AL amyloidosis in 2020. Hematology Am Soc Hematol Educ Program. 2020;2020(1):363-371. https://pubmed.ncbi.nlm.nih.gov/33275753/