Endocrine Abstracts

IgG4-related disease (IgG4-RD) is a fibro-inflammatory, immune-mediated, systemic disease usually presenting with tumefactive lesions and a subacute onset mimicking malignancy. A subset of autoimmune thyroid pathologic conditions can be incorporated in the spectrum of IgG4-RD. In some cases of Hashimoto’s Thyroiditis (HT) a rich IgG4-positive plasma cell infiltration has been described, and a marked storiform fibrosis is typical of the fibrotic variant of HT (FVHT) and of Riedel’s Thyroiditis (RT). In addition, the serum levels of IgG4 have been demonstrated to correlate with activity and severity of Graves’ orbitopathy (GO). Finally, IgG4-RD should be considered in the differential diagnosis of Graves’ like orbitopathy. The pathogenesis of IgG4-related thyroid diseases is poorly understood, but an autoimmune process resulting from genetic and environmental factors is hypothesized to play a pivotal role. Whether or not IgG4 have a direct pathogenic effect still remains to be ascertained, because infiltrating IgG4-positive plasma cells might only represent an epiphenomenon. The diagnostic criteria for specific IgG4-related thyroid diseases rely on histology. Thus, tissue biopsy is mandatory for a correct clinical assessment. Lympho-plasmacytic infiltrate, storiform fibrosis and obliterative phlebitis are the histologic hallmarks that confirm the clinical suspicion. The measurement of serum IgG4 levels may contribute to the diagnostic workup, and specific cut-offs have been propose in thyroid IgG4-RD. However, IgG4 serum negative patients do exist. Thus, the presence of high levels IgG4 in serum is not necessary to diagnose thyroid IgG4-RD. On the other hand, monitoring serum IgG4 levels can demonstrate treatment response or disease activity. Management options are both medical and surgical, depending on which condition has been diagnosed. Generally, glucocorticoids are the first line therapy and allow reducing the progression of the disease, while surgical management has been performed only in rare cases.