Abstract
Cardiac immunoglobulin light chain (AL) amyloidosis classically presents with biventricular heart failure and increased wall thickness. Recurrent unilateral pleural effusion as the inaugural manifestation is rarely recognized, and grade 3 99mTc-pyrophosphate (PYP) uptake is conventionally attributed to transthyretin amyloidosis (ATTR) amyloidosis. We describe a 66-year-old woman with treatment-resistant heart failure with preserved ejection fraction who presented with refractory pleural effusion requiring three large-volume thoracenteses. Echocardiography showed concentric hypertrophy with apical-sparing strain, and PYP scintigraphy demonstrated grade 3 myocardial uptake. Serum free light chains revealed a markedly elevated lambda fraction (33,562 mg/L) with a profoundly suppressed kappa-to-lambda ratio (0.001), and bone marrow biopsy confirmed coexistent multiple myeloma. First-line plasma cell-directed chemotherapy was initiated, but the patient died of septic shock and multi-organ failure 60 days after admission. This case illustrates two underrecognized phenomena: refractory unilateral pleural effusion as an inaugural feature of AL amyloidosis, and PYP-positive scintigraphy mimicking ATTR despite biochemically confirmed AL disease. Plasma cell dyscrasia must be excluded before any PYP-based diagnosis of ATTR amyloidosis is accepted, and refractory unilateral pleural effusion in a patient with diuretic-resistant heart failure warrants systematic evaluation for cardiac amyloidosis.