A 22 year old female was diagnosed with Graves’ disease (GD) with ocular manifestations eight months following her first dose of alemtuzumab prescribed for refractory relapsing-remitting multiple sclerosis (RRMS). She underwent a total thyroidectomy, and her TSH receptor antibody (TSHrAb) levels remained elevated. She had progression of her ocular disease with marked proptosis and associated exposure keratopathy.
Alemtuzumab is a humanised monoclonal antibody targeting CD52, a transmembrane protein expressed in T and B cells, which reduces relapse rate and disability progression among patients with RRMS.(1-2) Shifts in lymphocyte kinetics lead to undesirable reconstitution autoimmunity.(3-5) The profound lymphopaenia within days of infusion depletes CD4+ T regulatory cells (80%), CD8+ T lymphocytes (>80%) and mature B lymphocytes (>85%). This is followed by repopulation of B-cells, CD8+ T-cells, and CD4+ T-cells in sequence over time (Figure 1).(6-7) The marked hyper-repopulation (180%) of immature B-cells and the slower repopulation of memory CD4+ T-cells and T regulatory cells predisposes to autoimmunity.(6-7)
Autoimmune thyroid disease is the most common reconstitution autoimmune disorder that develops in patients treated with alemtuzumab; up to 70% of patients who develop thyroid dysfunction have GD.(3) Treatment options for alemtuzumab-induced GD include anti-thyroid medications, radioactive iodine therapy and surgery.
The TSHrAb occurs in 30-40% of these patients, and interestingly, TSHrAb in patients with alemtuzumab-induced GD can be stimulatory, inhibitory or neutral, making the disease course difficult to predict.(3) Up to 15% of these patients have a fluctuating course of disease, transitioning from a hyperthyroid to a hypothyroid state and vice versa.(3)
Graves’ eye disease is rare; only seventeen cases have been reported in the literature (2 moderate; 6 severe).(5) However, this could be an underestimate as routine ophthalmological assessment was not performed in all patients.
Figure-1. Time-course repopulation of lymphocytes in patients treated with alemtuzumab.