Hashimoto’s thyroiditis manifesting as IGG4 related disease in a thyroid remnant following total thyroidectomy for grave’s disease

IgG4 related disease (IgG4-RD) is now a widely recognised multi-organ system disease and is an emerging entity characterised by a diffuse or mass forming inflammatory reaction. Recent reports show that it can involve various organs including thyroid and that there is a unique subtype of Hashimoto’s thyroiditis, termed IgG4 thyroiditis, which is histopathologically characterised by lympho-plasmacytic infiltration, fibrosis, increased numbers of IgG4-positive plasma cells, and may have high serum IgG4 levels. Furthermore, IgG4 thyroiditis and non-IgG4 thyroiditis present different clinical features, with IgG4 thyroiditis being more prevalent in males, closely associated with rapid progress, subclinical hypothyroidism, higher levels of circulating antibodies, and more diffuse low echogenicity. We report a case of a 46-year-old woman with Hashimoto’s thyroiditis with histopathological features of fibrosing variant of Hashimoto’s thyroiditis and IgG4 related disease in a remnant thyroidectomy, 6 years after total thyroidectomy for Grave’s disease. It is not unusual for Grave’s disease and Hashimoto’s thyroiditis to coexist or follow one another. Awareness of clinico-pathological and possible radiological features of IgG4 related subset of Hashimoto’s thyroiditis would help better diagose this entity, rationalise treatment and avoid surgical options to diagnose and treat this variant.