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Aileen Sy, Rona Silkiss; Serum Total IgG and IgG4 Levels in Thyroid Eye Disease. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4726.
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IgG4-related disease (IgG4-RD) has recently been recognized as an etiology of previously described cases of orbital inflammatory disease or pseudotumor. The most common orbital inflammatory disease is thyroid eye disease (TED). The authors sought to evaluate total IgG and IgG4 levels in a TED population to determine if a subset of this population demonstrated latent IgG4-RD. Additionally, the relationship between total IgG, IgG4 and TSI levels was evaluated.
TED patients evaluated in the practice of one author between December 2013 and July 2014 were reviewed. Patients with total and IgG subclass and thyroid function tests were included in the study.
Of 19 patients studied, three were found to have elevated serum IgG4 levels by current criteria. All three patients presented with proptosis, extraocular muscle enlargement on MRI and elevated TSI, but no other systemic findings. One patient had elevated IgG4 and IgG4: total IgG ratio, positive by IgG4-RD criteria. The IgG4 levels of the remaining two patients were not positive by IgG4-RD criteria, but were positive by IgG4: total IgG ratio. In all patients, elevated IgG4 levels were not reflected in the total IgG levels. Additionally, elevated TSI levels were not reflected in levels of total IgG or any particular subclass of IgG.
We measured the serum IgG4 and IgG4: total IgG levels in patients with TED. Measurement of these levels in TED patients specifically has not been previously reported. Total IgG levels were not an adequate proxy for either IgG4 or TSI elevation. The results of this study suggest there may be a subpopulation of TED patients with elevated IgG4 without other systemic findings to suggest a type of IgG4-RD. This subpopulation of TED may be responsive to rituximab selectively. Further immunologic evaluation of TED patients may provide insight into the pathogenesis of the disease and aid in the selection of novel biologic therapy.
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