AL Amyloidosis Presenting as Hematochezia and a Colonic Mass

Abstract

AL amyloidosis (ALA) is an unusual result of a plasma cell dyscrasia, with an incidence of 8/106, that usually presents with renal, cardiac or hepatic findings. Tissue damage results from deposition of amyloid protein, which is derived from immunoglobulin light chains. ALA only rarely presents with lumenal GI findings. We report an 81 year old woman with a several month history of left lower quadrant pain, hematochezia, iron deficiency anemia, and constipation. The onset of abdominal pain preceded the other symptoms by 18 months. She had a significant PMH of MI, nephrectomy several years prior for renal cell cancer, and multi-infarct dementia. Colonoscopy revealed marked sigmoid diverticulosis with significant angulation. A near-obstructing, hemorrhagic, necrotic mass was noted in the mid sigmoid. Passage of the endosope beyond the mass was deferred due to concern for perforation. Multiple biopsies were obtained. The chief endoscopic differential diagnoses were colon carcinoma, inflammatory mass associated with diverticulitis, and mass effect secondary to colonic ischemia. CT scan was unremarkable. Intraoperative findings mirrored the endoscopic appearance. Pathologic examination of the resection specimen revealed an area of submucosal hemorrhage and ischemic necrosis. No evidence of carcinoma was noted. The walls of submucosal arteries were markedly thickened by deposition of an amorphous substance suspicious for amyloid. Congo red stains confirmed this substance as amyloid. The urine immunofixation electrophoresis (IFE) for the detection of Bence Jones proteins revealed free lambda monoclonal light chains. Immunostain revealed prominent staining of the arterial walls with antibody to lambda light chains. The development of the colonic mass lesion was probably related to ischemic necrosis and hemorrhage, which were a consequence of vascular damage by amyloid deposition. Although her chief manifestations were gastrointestinal, the urine IFE suggested systemic involvement. It is possible that she would have developed more typical manifestations over time, had she survived for longterm follow up. Subclinical ALA features were not explored due to a complicated post-operative course. In summary, this case illustrates an unusual presentation of ALA which mimicked much more common disorders such as colon carcinoma and diverticulitis.