A Case of Probable IgG4-related Small Intestinal Pseudotumor in a 92-year-old Woman

Abstract

A 92-year-old woman presented with abdominal pain, and computed tomography showed a mass lesion with a contrast effect at the end of the ileum and a dilated bowel. The diagnosis of obstructive ileus due to a small intestinal tumor was made, and an open ileal resection was performed. The resected specimen showed narrowing of the ileum 7 cm from the distal end of the ileum with serosal traction and paving stone-like mucous membrane elevation on the anorectal side, but no ulcerative lesion suggestive of carcinoma was observed. Histopathological examination showed heavy infiltration of lymphocytes and IgG4-positive plasma cells mainly in the deep mucosa and floral mat-like fibrosis. Immunostaining showed 32 IgG4-positive cells in a high-power field, with an IgG4-positive cell/IgG-positive cell ratio of 51.6%. The postoperative serum IgG4 level was 23.8 mg/dl, which was within the reference range. Although the patient was considered to have probable IgG4-related disease based on the diagnostic criteria, other neoplastic lesions were negative, and IgG4-related small intestinal pseudotumor was strongly suspected. Five cases of IgG4-related disease involving the small intestine, including four previously reported cases and an autopsy case, are reported.