A retrospective study of chronic Iymphocytic thyroiditis' relation with IGG4-related disease

IgG4-Related disease (IgG4-RD) is a newly recognised autoimmune disease characterized with fibrosis and increased IgG4-positive plasma cells in dense lymphoplasmocytic infiltration which involves many organ systems. Chronic lymphocytic thyroiditis is a histopathological description which includes many diseases that show lymphocyte infiltration in the thyroid gland. In the literature, there are publications showing that IgG4-RD can involve the thyroid gland. As a result of this involvement, a new entity called IgG4-Thyroiditis is defined. The aim of this study was to investigate the thyroid tissues of patients with chronic lymphocytic thyroiditis and immunohistochemically divide them as IgG4-related and not IgG4-related; and investigate histopathological, serological and clinical differences of these two groups. In our study, 84 patients diagnosed with chronic lymphocytic thyroiditis between 2017-2019 at Uludağ University Faculty of Medicine Pathology Department were examined and immunohistochemically divided into two groups as IgG4-related and unrelated. In the 9 cases evaluated as IgG4-related as opposed to other 75 cases: immunohistochemically number of IgG4-positive plasmocytes, IgG4 / IgG-positive plasmocyte ratios (p<0.0001, p<0.0001 respectively); histopathologically lymphoplasmocytic infiltration, fibrosis (p<0.0001, p<0.0001 respectively); serologically anti-Thyroid peroxidase and anti-Thyroglobulin levels (p<0.0001, p<0.0001 respectively); clinically, a significant increase in the frequency of hypothyroidism (p<0.0001) was detected. There was no significant difference between lymphoid follicle formation, accompanying benign lesions, thyroid gland weights, age and gender. In conclusion, it was found that IgG4-Thyroiditis has significant histopathological, immunohistochemical, clinical and serological differences compared to the rest of chronic lymphocytic thyroiditis. In order to be accepted as a new thyroiditis group, it is necessary to examine the subject with new studies that will reveal genetic and immunological differences.