LAUSR

Abstract Introduction: Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a rare autoimmune disorder involving 1 or multiple organs, most commonly the pancreas, lacrimal glands, and salivary glands. However, IgG4-related sclerosing mesenteritis (SM) involving the small-bowel mesentery is rare. Given that IgG4-related SM usually mimics the imaging characteristics of mesenteric malignancies, its preoperative diagnosis remains challenging. In addition, no specific consensus has been reached regarding the treatment of IgG4-related SM. Therefore, a better understanding of the characteristics, treatment, and prognosis of IgG-related SM is urgently needed. Herein, we report a rare case of IgG-related SM. Patient concerns: A 67-year-old man was admitted to our hospital after incidental detection of an abdominal mass on ultrasound imaging, although he reported being generally well. The findings on triple-phase abdominal computed tomography were highly consistent with a malignant mesenteric tumor. Diagnoses: The hallmark histopathological features along with elevated levels of IgG4 (145 mg/dL) and imaging findings were indicative of IgG-related SM. Interventions: The patient was treated surgically. Postoperative histopathological examinations exhibited tissue infiltration with lymphocytes and IgG4-positive plasma cells, as well as fibrosis. Outcomes: Ten days after surgery, the patient was discharged from the hospital, and did not show any clinical sign of IgG-related SM within 1-year follow-up. Conclusion: This case highlights the mesentery as an uncommon site of involvement as well as how early IgG-related SM can be completely asymptomatic. Thus, this study has advanced our knowledge of IgG-related SM and may improve treatments for similar conditions.