A case report of gastric amyloidosis due to multiple myeloma mimicking gastric cancer

BACKGROUND: Gastrointestinal (GI) amyloidosis is a rare complication of multiple myeloma (MM). Due to its nonspecific clinical presentation and endoscopic appearance, an early and accurate diagnosis of GI amyloidosis is difficult. Here, we report a case of GI amyloidosis due to MM, which initially presented as GI manifestations mimicking gastric cancer. CASE PRESENTATION: A 68-year-old woman presented to the hospital with a 6-month history of anemia, coupled with a recent onset of poor appetite and vomiting for 10 days. Esophagogastroduodenoscopy revealed a gastric antrum mucosal bulge that appeared on visual inspection to be a tumor. As a result, gastric cancer was suspected. However, gastric antrum biopsies demonstrated mild chronic superficial gastritis and esophageal biopsies demonstrated moderate-to-severe atypical hyperplasia of the squamous epithelium. A second endoscopy revealed massive gastric retention and a gastric antrum mucosal bulge with surface erosion. Ultimately, an upper GI tract biopsy demonstrating positive Congo red staining and a bone marrow biopsy indicating plasmacytosis confirmed the diagnosis of gastric amyloidosis due to MM. CONCLUSION: This case demonstrates that MM should be considered in patients with nonspecific GI manifestations, and in such cases, a biopsy with Congo red staining should be considered to confirm GI amyloidosis. Early detection of GI amyloidosis will ultimately improve outcomes for these rare patients.