Colonic Amyloidoma: A Rarely Encountered Finding

Abstract

Amyloidosis is a systemic disease characterized by the extracellular deposition of abnormal protein fibrils throughout the body that disrupts normal tissue architecture and function. It can present in many different forms, but the most common form that affects the gastrointestinal tract (GIT) is amyloid light-chain (AL) amyloidosis. Although amyloid deposition in the GIT is not uncommon, less than 50% will develop GI symptoms including GI dysmotility, malabsorptive diarrhea, spontaneous hemorrhage, and pseudo-obstruction. Early diagnosis of AL amyloidosis is essential because most cases are diagnosed late and associated with a poor prognosis. If left untreated it can carry median 1-year mortality rate of approximately 50%. Identifying the classic findings of AL amyloidosis during endoscopy should prompt further evaluation for disease. Our patient is a 54-year-old man with a past medical history significant for AL amyloidosis diagnosed on renal biopsy, who presented with worsening hematochezia. He also reported recurrent abdominal pain, a 60-pound weight loss, chronic diarrhea, and recurrent syncope for the last 4 months. Hemoglobin was 8.4 g/dL on admission. Colonoscopy revealed multiple large and small hemorrhagic polypoid lesions. The largest lesion filled approximately 75% of the colon. Multiple blood clots were also identified, but no active bleeding was seen during endoscopy. Endoscopic biopsies were not pursued given significant bleeding risk and prior diagnosis of AL amyloidosis. AL amyloid deposition within the vascular walls of the GIT increases vessel fragility and can result in hemorrhage beneath the lamina propria, forming submucosal hematomas. During endoscopy, submucosal hematomas appear purple and have a polypoid appearance with a shelf-like base. Other common findings during endoscopy include: mucosal ulcerations, intestinal erosions, yellowish plaque-like infiltrative lesions, and thickened mucosal folds. Rarely, as evident in our case, patients may have tumor-forming deposits of amyloid called amyloidomas, which can be wrongly diagnosed as a primary or metastatic GI malignancy. Given the poor prognosis associated with AL amyloidosis, recognizing common endoscopic findings should prompt the endoscopist to maintain a high index of suspicion and diagnose amyloidosis to improve overall prognosis.Figure: Endoscopy Findings.