Gastric Outlet Obstruction Due to Gastric Amyloidosis Mimicking Malignancy in a Patient with Ankylosing Spondylitis
A 65-year-old woman was referred to us because of abdominal distention, nausea, and vomiting that had been occurring for a month. Her medical history includes a diagnosis of ankylosing spondylitis 1 year ago, and she had been taking celecoxib daily. Physical examination revealed decreased bowel sounds and direct tenderness in the lower abdomen. Complete blood cell count showed a leukocyte number of 7,470/µL, hemoglobin of 8.8 g/dL, and platelet count of 301,000/mm3. Her blood chemistry values were as follows: total protein, 6.1 g/dL; albumin, 3.1 g/dL; total bilirubin, 0.4 mg/dL; aspartate aminotransferase, 26 U/L; alanine aminotransferase, 16 U/L; alkaline phosphatase, 368 U/L; blood urea nitrogen, 16.6 mg/dL; creatinine, 1.4 mg/dL; erythrocyte sedimentation rate, 79 mm/hr; and C-reactive protein, 2.8 mg/dL. Blood coagulation test revealed a prothrombin time/activated partial thromboplastin time of 11.8/29.5 seconds. Abdominal radiography showed a huge gastric shadow with a large amount of food materials in the gastric lumen. Abdominal computed tomography showed a large amount of retained food materials in the stomach and diffuse wall thickening of the gastric antrum (). Endoscopy revealed marked edema of the mucosa, multiple ulcerations, and luminal narrowing and limited distensibility of the gastric antrum (). Endoscopy also showed pyloric stenosis with ulceration (), but endoscopic mucosal change was not observed in the duodenum (). We performed endoscopic biopsies of the gastric antrum and the duodenum, which revealed the deposition of eosinophilic amorphous materials in the lamina propria and the submucosa in the stomach but not in the duodenum on hematoxylin and eosin staining (), and the accumulation of apple-green materials in the lamina propria and the submucosa in the stomach on Congo red staining (). Electron microscopy showed amyloid fibrils in the subepithelial layers (). The histological findings were compatible with amyloidosis, and the amyloid was identified as the AA type on immunohistochemical testing with monoclonal antibodies specific to serum amyloid A protein. Colonoscopy with random biopsies showed no colonic involvement by the amyloidosis. Bence-Jones proteins were present in urine, but an M-peak was not found in serum. Moreover, there were no abnormalities on bone marrow biopsy. Her final diagnosis was amyloidosis secondary to ankylosing spondylitis presenting with gastric outlet obstruction. Subtotal gastrectomy was recommended because of the worsening obstruction symptoms; however, she refused surgery and wanted to be transferred to another hospital. Three months later, she died of aspiration pneumonia during medical treatment.