Clinical and immunological changes in patients with active moderate-to-severe Graves' orbitopathy treated with very low-dose rituximab.

INTRODUCTION

Glucocorticoids represent the therapy of choice for active and moderate-to-severe Graves' orbitopathy (GO). In some patients, rituximab, a monoclonal antibody against the cluster of differentiation (CD) 20 receptor of B-lymphocytes, can serve as a second-line or an alternative treatment. The effect of very low-dose of rituximab on the clinical activity of GO and corresponding clinical or laboratory changes is reported.

MATERIAL AND METHODS

Changes of Clinical Activity Score (CAS) for GO, proptosis, levels of thyroid-stimulating hormone receptor antibodies, and depletion of CD19+ and CD20+ B-lymphocytes were determined in ten patients (two men and eight women) with active moderate-to-severe GO treated with a single 100-mg dose of rituximab. Correlations between differences of clinical and laboratory parameters were performed.

RESULTS

A significant decrease of CAS was found during subsequent examinations compared to the baseline values. A significant depletion of CD19+ and CD20+ B-lymphocytes was detected after rituximab administration. Differences between follow-up and baseline levels of CD20+ positively correlated with differences in CAS after six (p < 0.05) and 12 months (p < 0.01). Differences in CD19+ levels correlated with differences in CAS after 12 months (p < 0.05) of the treatment. Two patients developed dysthyroid optic neuropathy (DON) requiring orbital decompression. No other rituximab side effects were reported during the whole study duration.

CONCLUSIONS

A single very low-dose of rituximab appears to be very well tolerated and effective enough to reduce clinical activity in active moderate-to-severe GO patients without impending DON.