Gastrointestinal Amyloidosis with Multiorgan Involvement: A Case Report

Background: Systemic immunoglobulin light-chain (AL) amyloidosis is an uncommon plasma cell dyscrasia caused by deposition of misfolded monoclonal light chains within tissues, resulting in progressive organ dysfunction. Although cardiac and renal involvement are well recognized, clinically significant gastrointestinal involvement is uncommon and frequently overlooked because patients present with nonspecific symptoms that mimic more prevalent gastrointestinal disorders. Delayed diagnosis contributes to substantial morbidity and mortality, particularly in patients with multiorgan disease. We report a case of biopsy-confirmed systemic AL (lambda) amyloidosis involving the gastrointestinal tract, tongue, and myocardium that illustrates the critical role of early tissue diagnosis and multidisciplinary management. Case Presentation: We report a case of a 79-year-old Caucasian man with systemic AL (lambda) amyloidosis involving the myocardium, tongue, and gastrointestinal tract. The patient presented with progressive macroglossia, dysphagia, weight loss, and diarrhea. Upper endoscopy revealed granular, friable mucosa in the gastric antrum. Biopsies demonstrated amyloid deposition confirmed by Congo red staining with apple-green birefringence under polarized light. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) verified AL (lambda) amyloidosis, and bone marrow biopsy revealed 35% - 40% lambda-restricted plasma cells, consistent with plasma cell myeloma. During hospitalization, the patient experienced recurrent ventricular arrhythmias requiring advanced cardiac life support and subsequent dual-chamber implantable cardioverter-defibrillator implantation. He was treated with a cyclophosphamide, bortezomib, and daratumumab (Dara-CyBorD) regimen, resulting in gradual improvement of gastrointestinal symptoms and stabilization of cardiac and hematologic parameters. Despite therapy, the patient ultimately succumbed to complications of advanced systemic AL amyloidosis. Conclusion: This case highlights the importance of maintaining high clinical suspicion for gastrointestinal amyloidosis in patients with unexplained gastrointestinal symptoms and systemic features such as macroglossia or cardiac involvement. Tissue biopsy with Congo red staining and LC-MS/MS analysis remains the diagnostic gold standard. Early recognition, targeted plasma cell-directed therapy, and multidisciplinary management are essential to improving outcomes in systemic AL amyloidosis with gastrointestinal involvement.