Fulminant Cardiac Light-Chain (AL) Amyloidosis: A Case of Rapid Multiorgan Collapse and the Diagnostic Urgency of the Difference Between Involved and Uninvolved Free Light Chains (dFLC)

Light-chain (AL) amyloidosis is a rare systemic disease that can affect multiple organs.Cardiac involvement is common and frequently determines prognosis and survival.Cardiac AL amyloidosis is a progressive infiltrative cardiomyopathy.We report an unusually rapid course of cardiac AL amyloidosis resulting in severe multiorgan failure.This case illustrates the diagnostic and therapeutic challenges associated with a rapidly progressive disease course.We present the case of a 54-year-old man admitted with decompensated heart failure.Physical examination demonstrated significant volume overload.Laboratory evaluation of blood and urine was indicative of an active monoclonal plasma cell disorder.Echocardiography revealed a left ventricular ejection fraction of 10-15% and severe left ventricular hypertrophy.Review of prior echocardiograms demonstrated a preserved ejection fraction of 50-55% four months earlier.Nuclear medicine single-photon emission computed tomography combined with computed tomography (NM SPECT-CT) demonstrated cardiomegaly and findings inconsistent with transthyretin amyloidosis, with a heart-tocontralateral lung (H/CL) uptake ratio of 1.17.CT of the abdomen revealed enlargement of multiple organs, including the heart, liver, spleen, and kidneys.The patient underwent multidisciplinary evaluation by cardiology, nephrology, gastroenterology, and hematology-oncology.A bone marrow biopsy was performed, and combination chemotherapy was planned.However, the patient developed recurrent tachyarrhythmias and bradyarrhythmias followed by cardiac arrest and died before treatment could be initiated.The patient progressed from preserved ejection fraction to death within four months.Extremely elevated immunoglobulin light chain levels likely contributed to rapid cardiac deterioration through both amyloid deposition and direct cytotoxic effects.Disease staging using biomarkers including brain natriuretic peptide, troponins, and the difference in free light chain (dFLC) values is helpful in recognizing aggressive AL amyloidosis biology and treatment urgency.The recurrent arrhythmias likely reflected advanced amyloid infiltration of the cardiac conduction system.This fatal and complex case underscores the importance of interdisciplinary management and prompt initiation of plasma cell-directed therapy.