A197 COLONIC AMYLOIDOSIS: A CAUSE OF RECURRENT HYPOVOLEMIA

Abstract Background Systemic amyloidosis is a multi-organ disease characterized by abnormal extracellular protein deposition. The most common type is primary (AL) amyloid relating to underlying plasma cell dyscrasias. Other major variants include secondary (AA) amyloid from chronic inflammation, dialysis related amyloid (DRA) with β2-microglobulin, and heritable protein mutations. Management of the underlying disorder can limit further organ damage; however, no definitive treatment exists for familial causes. While uncommon, gastrointestinal involvement is variable and can cause asymptomatic infiltration, liver impairment, bleeding, or chronic diarrhea. Aims To discuss an unusual case of gastrointestinal amyloidosis as a cause of recurrent diarrhea and hypovolemic shock. Methods The patient records were examined, and a review of the literature was performed. Results An 87-year-old male with dementia, coronary artery disease and end stage renal disease from PCKD presented in hypovolemic shock. He had a two-week history of gradual onset, non-bloody, watery diarrhea with up to 20 bowel movements daily. He denied fever, sick contacts, travel, or recent antibiotic use. He had previously foregone endoscopy for a remote history of self-resolved hematochezia. Examination was notable for an uncomplicated inguinal hernia. Labs showed an anion-gap metabolic acidosis but no leukocytosis. He initially received iv hydration, vasopressors, and empiric antibiotics. CT showed diffuse wall thickening of the terminal ileum, colon and rectum with relative sigmoid sparing concerning for enterocolitis. Stool culture grew C. albicans, but C. difficile toxin and Ova and Parasite PCR were negative. He clinically improved with loperamide and was discharged only to be readmitted four days later with recurrent diarrhea and hypovolemia. Repeat cultures were negative. Endoscopy showed diffuse well-demarcated clean-based ulcers and colonic edema. Biopsies excluded viral causes but showed a classic appearance of apple-green birefringence on Congo red staining suggesting amyloid deposition. Raised light chain immunoglobulins and lysozyme on proteomic analysis indicated either AL or a heritable amyloid but excluded AA and DRA. Full diagnostic criteria for AL were not met as free light chain ratio was preserved without clear monoclonality. While his diarrhea again improved, next-of-kin opted for palliative care due to repeated admissions for delirium and generalized deterioration. Conclusions This case was indicative of atypical AL amyloidosis versus a rare lysozyme mutation involving renal and GI systems. AL amyloid has a classic appearance on special stains and mass spectrometry that distinguishes it from most subtypes, however, given elevated lysozyme levels further genetic analysis is needed to guide management. In the appropriate clinical context, gastrointestinal amyloidosis can be considered as a rare cause of recurrent unexplained diarrhea. Funding Agencies None

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