Navigating the labyrinth: Phenotypes of IgG4-related disease.

We report a case of an elderly female with subacute submental neck swelling, dry cough, and a history of significant weight loss. Unexpectedly, a left submandibular chronic sialadenitis was noted on ultrasound of the neck, along with a thyroid nodule that, on biopsy, showed lymphocytic infiltration. High-resolution computed tomography of the lungs revealed multifocal irregular consolidations with lymphadenopathy, and possible infective causes, including tuberculosis, were ruled out after a thorough microbiological evaluation. It was only after a positron emission tomography-guided lung biopsy with specialized immunohistochemical staining was performed that the diagnosis of IgG4-related disease (IgG4-RD) was confirmed. Our patient exhibited overlapping features of head and neck-limited and Mikulicz/systemic phenotype of IgG4. In this case report, we highlight the clinical phenotypes of IgG4-RD, their respective differential diagnoses, and discuss our approach to this challenging case.