Graves' disease with spontaneous resolution following ocrelizumab in primary progressive multiple sclerosis.

Immune reconstitution therapies (IRT), which include antibody-based cell-depleting therapies targeting CD52+ (alemtuzumab) or CD20+ (rituximab, ocrelizumab) leukocytes, are approved for the treatment of multiple sclerosis. Thyroid autoimmunity is a common adverse effect of alemtuzumab treatment, Graves' disease (GD) being the most prevalent manifestation. To date, thyroid autoimmunity events have not been reported with CD20-targeting monoclonal antibodies. A 59-year-old woman with primary progressive multiple sclerosis with no prior personal history of thyroid disease or autoimmunity, was diagnosed with GD 6 months following the first ocrelizumab infusion. She was asymptomatic and had no signs of ophthalmopathy. Due to the temporal association of GD diagnosis with ocrelizumab infusion, absence of symptoms and our experience with alemtuzumab-induced GD, we decided for an active surveillance strategy and antithyroid drugs were not started. She underwent spontaneous resolution of hyperthyroidism with thyroid-stimulating hormone (TSH) receptor antibodies (TRAb) negativity and a mild and transitory period of subclinical hypothyroidism, while she continued the biannually ocrelizumab administration schedule. To present date, she has maintained close clinical and biochemical surveillance with normal TSH, free thyroxine (fT4) and free triiodothyronine (fT3) levels and undetectable TRAb. This is the first case of GD reported after ocrelizumab administration. The timing, onset and course of this case is similar to alemtuzumab-induced GD, usually interpreted as an "immune reconstitution syndrome"; however, ocrelizumab cell count depletion is inferior in severity, cell population affected and duration of depletion. This case highlights the importance of pre-screening and follow-up with thyroid function tests in patients treated with ocrelizumab. As a novel therapeutic antibody, further investigation is required to unravel the causes of thyroid autoimmunity.