Key result
Endomyocardial biopsy with proteomics resolves discordant testing by definitively confirming cardiac AL lambda amyloidosis.
Why the study?
Accurate differentiation of AL from ATTR amyloid cardiomyopathy is critical due to differing treatments, but discordant extracardiac amyloid findings may confound diagnosis.
Does endomyocardial biopsy with proteomic analysis accurately subtype cardiac amyloidosis in patients with discordant extracardiac amyloid deposits and monoclonal gammopathy?
Case Report (n=1)
Does endomyocardial biopsy with proteomic analysis accurately subtype cardiac amyloidosis in patients with discordant extracardiac amyloid deposits and monoclonal gammopathy?
When extracardiac biopsies show discordant amyloid subtypes or bystander proteins in a patient with monoclonal gammopathy, endomyocardial biopsy with proteomic analysis remains essential for definitive cardiac amyloid subtyping to direct therapy.
Endomyocardial biopsy proteomics may resolve discordant amyloid subtyping; leaves open need for prospective validation before routine use.
BACKGROUND: Accurate differentiation of immunoglobulin light-chain (AL) from transthyretin (ATTR) amyloid cardiomyopathy is critical, as misclassification may delay appropriate therapy and worsen outcomes. CASE SUMMARY: An 80-year-old woman with incidental gallbladder AL lambda and ApoA-IV amyloid deposits had elevated cardiac biomarkers and lambda monoclonal gammopathy. Bone marrow biopsy demonstrated AL and ATTR deposits. Echocardiography showed increased wall thickness, apical-sparing strain, and elevated filling pressures. Given these discordant findings, endomyocardial biopsy (EMB) was performed; proteomic analysis confirmed AL lambda deposition without ATTR, prompting anti-plasma cell therapy. DISCUSSION: This is a rare case of mixed extracardiac amyloid required EMB with proteomic analysis to resolve discordant findings and confirm AL cardiomyopathy. TAKE-HOME MESSAGES: Amyloid cardiomyopathy subtyping is essential because AL and ATTR amyloidosis treatment differ fundamentally. Underrecognized codeposited "bystander" proteins may confound typing; therefore, discordant extracardiac findings may not represent the myocardial subtype. When uncertainty persists, particularly with monoclonal gammopathy, EMB is essential to define cardiac amyloid subtype.
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Coderre et al. (2026) conducted a case report in Amyloid cardiomyopathy (n=1). Endomyocardial biopsy with proteomic analysis was evaluated on Myocardial amyloid subtype determination. Endomyocardial biopsy with proteomic analysis definitively confirmed AL lambda-type amyloid deposition without ATTR in the myocardium, resolving discordant extracardiac findings.
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