Localized Gastrointestinal Light Chain (AL) Amyloidosis Under Surveillance for Five Years: A Case Report.

Amyloidosis, characterized by the deposition of abnormal protein fibrils in organs, is classified as systemic or localized. Amyloid light chain (AL)-type localized amyloidosis is uncommon, particularly when confined to the gastrointestinal tract. Herein, we report a case of localized gastrointestinal AL-type amyloidosis that was incidentally detected and remained endoscopically and clinically stable over a 5-year follow-up period. The patient, a man in his 40s, had undergone a colonoscopy for colorectal cancer screening, during which scattered erosions were detected in the colon. Amyloid deposits were identified on biopsy. No cardiac or renal involvement, or evidence of multiple myeloma, was found. He was ultimately diagnosed with localized AL-type gastrointestinal amyloidosis. Following diagnosis, the patient underwent regular surveillance with transoral and transanal small-bowel endoscopy. No endoscopic progression or gastrointestinal symptoms were observed during the follow-up period, and the patient remained asymptomatic. This case suggests that conservative observation may be reasonable in carefully selected patients after exclusion of systemic involvement.