Bridging Diagnostic Gaps in AL Cardiac Amyloidosis

AL cardiac amyloidosis (CA) is challenging to diagnose due to limitations of biopsy and conventional imaging. Endomyocardial biopsy (EMB) can yield false negatives, and 99m Tc-pyrophosphate scintigraphy is less reliable for AL amyloidosis. We report a 56-year-old man with progressive dyspnea, palpitations, and macroglossia, in whom echocardiography revealed hypertrophic cardiomyopathy with reduced ejection fraction. Cardiac MRI, bone marrow biopsy (BMB), and EMB were inconclusive, while PYP scintigraphy was equivocal. 68 Ga-FAPI-46 PET/CT demonstrated intense myocardial uptake, prompting a repeat BMB confirming AL amyloidosis. This case underscores the emerging role of FAPI PET/CT in clarifying diagnosis after an equivocal workup, enabling targeted therapy.