Clinically Isolated IgG4-Related Disease of the Larynx: A Rare Cause of Progressive Dysphonia.

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a systemic immune-mediated fibroinflammatory condition marked by lesions with dense IgG4-positive plasma cell infiltrates. While it is commonly associated with salivary and pancreatic involvement, isolated laryngeal involvement is extremely rare, with an estimated 15 documented cases. This report describes the case of a 66-year-old female presenting with persistent dysphonia who was found to have isolated IgG4-RD of the larynx, highlighting the diagnostic complexity and novel presentation. The patient presented to the primary care office with persistent and progressive dysphonia following an upper respiratory infection. Laryngoscopy demonstrated a supraglottic submucosal mass. Biopsy showed chronic inflammation, fibrosis, and squamous metaplasia without dysplasia. She was later referred to a tertiary facility for further investigation due to the progressive nature of her symptoms and concern for airway compromise. At that time, the prior biopsy specimen underwent immunohistochemical review for the first time. Immunohistochemical analysis revealed dense lymphoplasmacytic infiltration, storiform fibrosis, and abundant IgG4-positive plasma cells, establishing the diagnosis of IgG4-RD of the larynx. She was initiated on systemic corticosteroids and transitioned to long-term azathioprine, resulting in symptomatic improvement and regression of the laryngeal findings. IgG4-RD of the larynx is a rare manifestation that can be challenging to diagnose. This report emphasizes the importance of immunohistochemical evaluation in patients whose biopsy results are nondiagnostic. Early recognition of IgG4-RD enables timely treatment, reduces the risk of airway compromise, and helps preserve laryngeal function.