S3805 Localized AL Amyloidosis of the Colon: A Rare Gastrointestinal Presentation

Introduction: Amyloidosis, a disease caused by fibril-forming proteins that gradually deposit in tissues, leading to cell damage and organ dysfunction. Amyloidosis manifest either systemically or less commonly locally as result of multiple precursor proteins. Very few cases of Localized GI amyloidosis have ever been reported. Our case represents an incidental asymptomatic amyloid polyp found on a routine cancer screening colonoscopy. Case Description/Methods: A 79-year-old man with a positive stool fecal DNA test with a subsequent colonoscopy that showed 6 sessile polyps located throughout the colon. They were excavated using forceps and cold/hot snare techniques. The polyps were benign in appearance and ranged in size from 1 mm to 12 mm. A single sigmoid polyp measuring 10 mm was positive for Congo red staining. After oncologic consultation to further rule out systemic amyloidosis, Testing showed a unremarkable complete blood count with a normal peripheral blood smear, normal Total globulin level 2.4 gm/dL, and unremarkable SPEP. Kappa free light chain was 23.2, Lambda 3 light chain 12.8 mg/dL, Kapp/Lambda ratio was 1.81. Bone marrow biopsy from posterior right iliac crest core biopsy with no definitive evidence of plasma cell neoplasm. FISH showing partial atypical CD56 expression. Congo Red on core biopsy with no amyloid deposition identified. Positron emission tomography -computed tomography with no evidence of FDG-avid malignancy or focal abnormality. Genetic testing for 40 gene mutations and TTR testing was negative. The patient was managed conservatively with a surveillance colonoscopy. Discussion: Case studies have shown the rare subtype of Localized GI amyloidosis. Grossly, this can be in the form of polyposis as in our case, perforations, pseudo-tumors or ulceration, either submucosal or mucosal. To the best of our knowledge, 4 cases were reported prior as colonic polyps with all involving amyloid light chain. or those cases of localized polyps’ expectant management is the best choice. Characterization of the clinicopathologic subtype often determines treatment. In a case, the colonic mass had a resemblance to cancer where with a positive apple core sign, hemicolectomy was performed. Another Case report used an endoscopic mucosal resection technique for the removal of the localized colonic amyloid polyp. Monitoring is often recommended as long-term complications can occur in the form of colonic dilatation, pseudo-obstruction, stricture, bleeding, volvulus, infarction, and perforation.