Duodenal stricture secondary to IgG4-related chronic sclerosing duodenitis-A case report with review of the literature.

Key Clinical Message: This case highlights the importance of a definite diagnosis of an IgG4-related chronic sclerosing duodenitis based on histological and radiological findings to rule out any malignancy in the mass. While dealing with patients having concentric duodenal thickening resulting in stricture formation, one should think of inflammatory etiology as well. IgG4-related disease is one of these inflammatory disorders where we see soft tissue thickening without a large mass or any associated lymphadenopathy as in our case. Abstract: Immunoglobulin G4-related disease (IgG4-RD) is distinguished as an infiltration of IgG-4-positive plasmacytes involving inflammatory lesions across multiple organs which is accompanied by raised IgG4 levels in the serum. Several inflammatory disorders are recognized as part of the IgG4-RD family based on shared histopathological features, which include Mikulicz's disease, chronic sclerosing sialadenitis, or Riedel's thyroiditis. Our case highlights a distinctive presentation of IgG4-related diseases; a 58-year-old man presenting with duodenal stricture highly suspicious of a duodenal mass/ampullary mass later found to be due to IgG4-related sclerosing duodenitis with negative malignancy on biopsy. We present the diagnostic challenges faced and relevant findings noted.