A Rare Presentation of IgG4-Related Sinusitis With Chronic Nasal Obstruction and Headache: A Case Report and Literature Review.

IgG4-related disease (IgG4-RD) is a systemic inflammatory condition characterized by tissue infiltration with IgG4-positive plasma cells and a tendency to form mass-like lesions in various organs. IgG4-related sinusitis, although a relatively rare manifestation of IgG4-RD, significantly impacts the paranasal sinuses. A 52-year-old man presented with persistent rhinorrhea, nasal obstruction, and headaches. He was diagnosed with IgG4-RD involving the bilateral nasal cavity, paranasal sinuses, submandibular glands, lacrimal glands, and parotid glands. We recently managed a case of IgG4-related sinusitis, which was successfully diagnosed and treated. This condition represents a distinct subset of chronic rhinosinusitis, with unique pathophysiological and clinical features. Accurate diagnosis and effective management of IgG4-related sinusitis require a high index of suspicion and a multidisciplinary approach.