Graves'-like orbitopathy: do not forget IgG4-related disease.

Abstract

ultrasonographic and/or serological evidence of autoimmune thyroid disease makes diagnosis of GO even more uncertain. Thus, if in typical cases imaging is confirmatory, then in doubtful circumstances it is mandatory. Many conditions may cause exophthalmos and/or extraocular muscle enlargement mimicking GO. Table 1 offers a list of these conditions, for some of which etiology is uncertain. IgG4-related disease is a recently described fibroinflammatory multiorgan disorder characterized by tumefactive lesions, lymphoplasmacytic infiltration with abundant IgG4-positive plasma cells, storiform fibrosis and frequently (but not always) elevated serum IgG4 levels (see [4] for an excellent and exhaustive review of this disease). Initially described in the context of autoimmune pancreatitis, IgG4-related disease may indeed affect several extrapancreatic sites, including the thyroid and the orbit. Riedel’s (fibrosclerosing) thyroiditis has been shown immunohistochemically to be comprised within the spectrum of IgG4-related disease [5]. The fibrous variant of Hashimoto’s thyroiditis might also be closely related to IgG4-related disease [6]. Graves’-like orbitopathy was described in a patient with autoimmune pancreatitis and very high serum IgG4 concentrations, in the absence of thyroid autoimmune disease or related thyroid dysfunction [7]. Clinical features were similar to those of moderate-to-severe and active GO. Imaging was characterized by enlarged extraocular muscles (with tendon sparing) and lacrimal gland, and expansion of the adipose tissue; there was an excellent response of orbital changes to intravenous glucocorticoids and orbital radiotherapy [7]. An additional case was described at the Mayo Clinic: the patient had a longlasting diagnosis of “GO”, treated many times with oral glucocorticoids because of repeated recurrences [8]. The patient was eventually submitted to orbital Graves’ orbitopathy (GO) affects about 25 % of patients with hyperthyroidism due to Graves’ disease [1], is usually mild and infrequently progressive [2, 3], although moderate-to-severe or (rare) sight-threatening forms do exist and require aggressive treatments [1]. In most cases, the onset of GO is temporally related to the onset of hyperthyroidism, but in some instances the orbital disease may precede or follow the onset of hyperthyroidism by months or years [1]. In addition, it is known that GO may less frequently develop in patients with euthyroid or hypothyroid Hashimoto’s thyroiditis [1]. The diagnosis of GO is simple and straightforward in the typical patient who, in addition to signs and symptoms of hyperthyroidism, has positive TSHreceptor antibody tests, bilateral eye symptoms (lacrimation, grittiness, photophobia, diplopia) and signs (exophthalmos, periorbital soft tissue swelling, ocular dysmotility, rarely visual defects). Diagnosis is confirmed by imaging studies showing enlarged extraocular muscles (with tendon sparing) and/or expansion of the orbital fibroadipose tissue [1]. Diagnostic problems arise particularly in those patients who are not hyperthyroid and have asymmetrical or unilateral orbital involvement. The presence of euthyroid/hypothyroid chronic autoimmune thyroiditis does not guarantee that orbital disease be related to GO; the absence of thyroid