Abstract:

Background:

Hashimoto thyroiditis(HT) is the most commonest form of autoimmune thyroiditis with heterogenous clinical presentation. Recently a type of Hashimoto thyroiditis with dense   lymphoplasmacytic  infiltration and marked fibrotic changes with  increased numbers of IgG4-positive plasma cells  and serum IgG4 have been reported in the literature and they have a close relationship to IgG4-related disease (IgG4-RD).On the basis of immunostaining for IgG4, HT was divided into an IgG4 thyroiditis group and a non-IgG4 thyroiditis group and their clinical and histopathological features were studied.

Aims and Objectives:

To categorize Hashimoto  thyroiditis into two subgroups  with reference to IgG4-positive plasma cell  infiltration and  to determine the histopathological characteristics of each group.

Materials and methods:

It was a retrospective cross sectional study for a period of  one and half  year. Cases which were histopathologically diagnosed as Hashimoto thyroiditis were included in the study. Immunohistochemistry marker done for IgG4 and the areas with the highest density of positive cells were evaluated.

Results:

Among the 13 cases of Hashimoto thyroiditis 8 cases  were subtyped into IgG4 thyroiditis group   and 5cases into non  IgG4 thyroiditis group based on immunohistochemistry. All the cases were females in both the groups and the age of presentation in IgG4 thyroiditis was younger when compared to non IgG4 thyroiditis .Histopathologically ,IgG4 thyroiditis showed marked fibrosis and moderate to severe lymphoplasmacytic infiltration with increased IgG4 positive plasma cell infiltration when compared to non IgG4 thyroiditis.

Conclusion:

Immunostaining of IgG4 can help in the  subtyping of  Hashimoto thyroiditis and are closely related with IgG4 related diseases.IgG4 Hashimoto thyroiditis presents with  a distinct histopathological features when compared to non IgG4 thyroiditis.