Rare coexistence of adult-onset asthma with periocular xanthogranuloma and Immunoglobulin G4-related disease

IgG4-related disease (IgG4-RD) is a systemic fibroinflammatory condition affecting multiple organs, including the orbit. Adult-onset asthma with periocular xanthogranuloma (AAPOX) is a rare subtype that may share histopathologic and immunologic features with IgG4-RD. We report a 61-year-old man with a history of asthma and pancreatitis who presented with recurrent bilateral eyelid swelling and ptosis. Elevated serum IgG4 levels and dense IgG4-positive plasma cell infiltration in orbital tissue supported the diagnosis of IgG4-RD with overlapping AAPOX features. The patient showed an initial response to corticosteroids, and early rituximab therapy contributed to sustained remission, despite a transient relapse during tapering. During follow-up, an incidental intramucosal carcinoma arising in a sigmoid colon polyp was detected. This case highlights the rare coexistence of AAPOX and IgG4-RD, emphasizing the importance of comprehensive systemic evaluation and malignancy screening in patients with atypical or relapsing presentations.