Ileocecal IgG4-Related Disease: A Case Report Mimicking Malignancy.

Immunoglobulin G4-related disease (IgG4-RD) is a chronic mass-forming inflammatory disease characterized by fibroblastic proliferation and mixed inflammatory cell infiltration. IgG4-RD can involve one or multiple organs, and the most commonly affected organs include the pancreas, salivary glands, and the orbit. We present a case of a 66-year-old man, with a history of sarcoidosis, who presented with an obstructing ileocecal mass highly suspicious for malignancy. After surgical resection and pathological and serological evaluation, a diagnosis of IgG4-RD was rendered. In the absence of other manifestations, preoperative diagnosis is challenging, and IgG4-RD may continue to be a diagnostic pitfall.