Immunoglobulin G4-related Disease of the Small Bowel: A Case of Long-term Remission Achieved by Surgical Resection without Maintenance Therapy.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disease. IgG4-RD can affect any organ system, including the pancreas, bile ducts, salivary glands, mesentery, and retroperitoneum. On the other hand, small intestine involvement is extremely rare. This paper describes a case of IgG4-RD involving the small bowel, particularly at the distal ileum. An 81-year-old female was admitted to the authors' hospital complaining of abdominal pain, dyspepsia, and hematochezia. The laboratory tests, including tumor markers and IgG4, were within normal limits. A colonoscopy did not show any abnormal findings. Abdominal computed tomography revealed segmental aneurysmal dilatation and wall thickening at the distal ileum, suggesting malignant conditions, such as small bowel lymphoma. The patient underwent an exploratory laparoscopy and ileocecectomy to differentiate a malignancy. A histopathology examination revealed dense lymphoplasmacytic infiltration, storiform fibrosis, and IgG4-positive plasma cells (>50 per high power field). The patient was finally diagnosed with IgG4-RD. The patient was followed up in the outpatient clinic for five years without recurrence. This paper suggests that a radical resection without maintenance therapy can be a treatment option, particularly when the IgG4-RD manifests as a localized gastrointestinal tract lesion.