ABSTRACT
Introduction: Systemic amyloidosis (SA) comprises a heterogeneous group of disorders characterized by extracellular deposition of misfolded protein fibrils, leading to progressive organ dysfunction. Amyloid A (AA) amyloidosis is a systemic disorder that may involve multiple organs, including the gastrointestinal tract, heart, and serosal surfaces. Case presentation: We report a middle-aged man with long-standing ankylosing spondylitis who presented with progressive dyspnea and marked functional decline. Laboratory evaluation demonstrated severe hypoalbuminemia, chronic kidney disease with severe albuminuria, and markedly elevated N-terminal pro-B-type natriuretic peptide (NT-proBNP) despite only mild high- sensitivity troponin elevation. Electrocardiography showed low QRS voltage with a pseudoinfarction pattern. Transthoracic echocardiography revealed concentric left ventricular hypetrophy, mildly reduced ejection fraction, an infiltrative myocardial appearance, and severely impaired global longitudinal strain disproportionate to the degree of systolic dysfunction. Gastrointestinal biopsies demonstrated Congo red-positive amyloid deposits with positive amyloid A immunostaining, confirming systemic AA amyloidosis. Conclusions: This case illustrates systemic AA amyloidosis as a rare but devastating complication of long-standing, poorly controlled ankylosing spondylitis. The combination of dyspnea with large serosal effusions, markedly elevated NT-proBNP disproportionate to troponin elevation, low-voltage electrocardiography, and left ventricular hypertrophy with severely impaired global longitudinal strain should raise suspicion for cardiac amyloidosis in patients with chronic inflammatory diseases and prompt timely diagnostic evaluation.