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

Objective: Previous study suggested IgG4 levels were associated with the development of Graves' ophthalmopathy (GO). The aims of the present study were to investigate the role of IgG4 levels in glucocorticoid (GC) treatment in GO patients.

Design: 69 GO patients were enrolled. Serum thyroid hormones, thyroid antibodies, IgG, IgG4, ophthalmological examinations and orbital MRI were performed. Furthermore, the clinical outcomes (a composite response endpoint including the clinical activity score (CAS), proptosis, vision, intraocular pressure, diplopia and lid width) after high-dose intravenous GC treatment in 32 active moderate-to-severe GO patients were compared.

Patients: 69 consecutive patients with GO were asked to participate in the study. 32 of 69 GO patients were treated with high-dose intravenous GCs.

Measurements: Measurement of serum IgG and IgG4, serum thyroid hormones and thyroid autoantibodies. An overall ophthalmic assessment was performed pretherapy (week 0) and post-therapy (week 12).

Results: 33.3% of GO patients (23/69) had elevated IgG4 levels. IgG4 levels were positively correlated with the severity and activity of GO. After GC therapy, IgG4, IgG4/IgG, vision and CAS were significantly improved 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 GCs treatment compare with normal IgG4 GO patients.