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AL vs ATTR Amyloidosis Differentiation — EECC MCQ

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HardCardiomyopathyAL vs ATTR Amyloidosis DifferentiationEECC

A 65-year-old woman presents with progressive heart failure, thickened ventricles (IVS 14 mm), biatrial dilatation, and a restrictive filling pattern on echocardiography. NT-proBNP is 6,500 pg/mL. Serum free light chains are normal. DPD scintigraphy shows no cardiac uptake. Cardiac MRI shows diffuse subendocardial LGE with elevated native T1 and ECV. What is the most likely diagnosis?

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Correct answer: B — AL amyloidosis

The key distinguishing feature is the negative DPD scintigraphy combined with positive CMR findings for amyloidosis. DPD scintigraphy is highly sensitive and specific for ATTR amyloidosis (>99% sensitivity); a negative scan effectively rules out ATTR. With normal serum free light chains, tissue biopsy (e.g. endomyocardial biopsy or fat pad aspirate) with Congo red staining and immunohistochemistry/mass spectrometry is essential to confirm AL amyloidosis, as serum free light chains can be normal in ~5% of AL cases. The CMR pattern (diffuse subendocardial LGE, elevated T1/ECV) is typical of cardiac amyloidosis but cannot distinguish AL from ATTR. AL amyloidosis requires urgent haematology referral for treatment.

Reference: ESC (2023): Guidelines on Cardiomyopathies