Kappa Light-Chain Amyloidosis Presenting as Recurrent Ascites: A Diagnostic Challenge

Introduction: Systemic light chain (AL) amyloidosis is a rare monoclonal plasma cell disorder marked by extracellular deposition of misfolded immunoglobulin light chains, often affecting renal, cardiac, and hepatic systems. While ascites is usually due to hepatic or cardiac dysfunction, its role as a primary manifestation of AL amyloidosis is rare. This case highlights the diagnostic complexity of unexplained ascites and the need to consider infiltrative causes. Case Description: A 69-year-old male with hypertension and stage III chronic kidney disease presented with fatigue, melena, and progressive abdominal distension. Exam showed tense ascites and bilateral 3+ pitting edema without jugular venous distension, hepatojugular reflux, or S3. Initial paracentesis showed high serum-ascites albumin gradient (SAAG ≥1.1 g/dL) and low protein, suggestive of portal hypertension. Repeat paracentesis revealed high SAAG with elevated protein, raising concern for cardiac ascites. However, echocardiography and right heart catheterization were unremarkable. Persistent nephrotic-range proteinuria and an M-spike on serum protein electrophoresis prompted further workup. Renal biopsy confirmed AL amyloidosis with kappa light chain restriction. Bone marrow biopsy supported systemic involvement. With no cirrhosis and normal cardiac studies, liver biopsy was performed and revealed amyloid deposition. Mass spectrometry confirmed AL (kappa)-type amyloid. The patient opted for palliative care after discussing prognosis and options. Discussion: This case illustrates the diagnostic challenges of AL amyloidosis presenting as recurrent ascites. A changing paracentesis profile and nondiagnostic cardiac workup necessitated liver biopsy. The case underscores the value of broad differentials and tissue biopsy when standard evaluation is inconclusive. Teaching Points: - Consider AL amyloidosis in recurrent ascites when hepatic and cardiac causes are ruled out. - Variability in ascitic fluid may reflect evolving or mixed pathology. - Tissue biopsy is essential for confirming systemic infiltrative diseases. - A stepwise diagnostic approach is key in identifying rare causes of ascites