S3731 Plaque Attack: When Amyloidosis Strikes the Colon

Introduction: Amyloidosis is a rare disorder marked by abnormal deposition of insoluble protein aggregates in tissues and organs, impairing function. Gastrointestinal (GI) involvement is more often seen in systemic forms than in localized disease. We present a rare case of localized GI amyloidosis presenting as persistent subacute diarrhea. Case Description/Methods: A 79-year-old man with a past medical history of coronary artery disease, trans-aortic valve replacement, rheumatoid arthritis, chronic obstructive pulmonary disease, end-stage renal disease on hemodialysis, and recent C. difficile colonization following prolonged antibiotic therapy, presented with a fever, vomiting, and diarrhea. He was admitted for gram-negative bacteremia and Influenza A pneumonia. Due to persistent subacute diarrhea, a comprehensive stool panel was obtained, revealing C. difficile colonization. Fecal elastase was measured at 71 μg/g and fecal calprotectin was elevated at 182 μg/g. He was maintained on oral vancomycin and initiated on loperamide. Due to persistent nausea, vomiting and a computed tomography (CT) scan of the abdomen and pelvis demonstrating diffuse proctocolitis, loperamide was discontinued. Subsequent colonoscopy revealed abnormal mucosa with patchy erythema in the ascending colon and edematous folds in the sigmoid colon, from which biopsies were obtained. Despite treatment with cholestyramine, rifaximin, pancrelipase, and diphenoxylate/atropine, the patient continued to experience refractory non-bloody diarrhea. Due to ongoing hypotension related to diarrhea and overall clinical decline, the patient ultimately elected to pursue home hospice care. Pathological analysis of colonic biopsies confirmed the diagnosis of amyloidosis. Discussion: GI amyloidosis remains a diagnostic challenge due to its overlap with more common conditions and lack of distinctive features. It can present as a broad spectrum of clinical manifestations, including weight loss, GI bleeding, altered bowel habits, and malabsorption. Its insidious onset and nonspecific nature of symptoms often result in delayed diagnosis. Histopathological analysis remains essential for definitive diagnosis. This case highlights the diagnostic challenge of GI amyloidosis, particularly in elderly patients with multiple comorbidities. Given the potential for substantial morbidity and mortality, timely diagnosis and appropriate management are critical. Optimizing symptom control and nutritional support can significantly enhance quality of life in affected individuals.