Alemtuzumab-induced thyroid eye disease successfully treated with a single low dose of rituximab

Introduction: Secondary thyroid autoimmunity, especially Graves' disease (GD), frequently develops in patients with multiple sclerosis (MS) following alemtuzumab treatment (ALTZ; anti-CD52). Thyroid eye disease (TED) can also develop, and rituximab (RTX; anti-CD20) is a suitable treatment. Case presentation: A 37-year-old woman with MS developed steroid-resistant active moderate-to-severe TED 3 years after ALTZ, that successfully responded to a single 500 mg dose of i.v. RTX. Before RTX peripheral B-cells were low, and were totally depleted immediately after therapy. Follow-up analysis 4 years post ALTZ and 1 year post RTX showed persistent depletion of B cells, and reduction of T regulatory cells in both peripheral blood and thyroid tissue obtained at thyroidectomy. Conclusion: RTX therapy successfully inactivated TED in a patient with low B-cell count derived from previous ALTZ treatment. B-cell depletion in both thyroid and peripheral blood was still present 1 year after RTX, indicating a likely cumulative effect of both treatments.