Clinical relevance of serum immunoglobulin G4 in glucocorticoid therapy of Graves' ophthalmopathy.

Objective Previous studies suggested IgG4 levels were associated with the development of Graves' ophthalmopathy (GO). The present study investigated the role of IgG4 levels in glucocorticoid (GC) treatment in GO patients. Methods Sixty-nine GO patients were enrolled. Serum thyroid hormones, thyroid antibodies, IgG, IgG4, ophthalmological examinations and orbital MRI were performed. The clinical outcomes (a composite response endpoint including the clinical activity score (CAS), proptosis, vision, diplopia, and lid width) after high-dose intravenous GC treatment in 32 active moderate-to-severe GO patients were compared. Results A total of 33.3% of GO patients (23/69) had elevated IgG4 levels. IgG4 levels positively correlated with GO severity and activity. After GC therapy, IgG4, IgG4/IgG, vision and CAS improved significantly in GO patients. Patients with high IgG4 levels had a significantly reduced extraocular muscle area (EOMs) and better clinical outcomes than patients with normal IgG4 levels. Conclusions Our results suggest a possible subgroup of elevated IgG4 GO patients with more severe ophthalmopathy and better response to GC treatment compared to normal IgG4 GO patients.