Immunoglobulin G4 related thyroid disorders: Diagnostic challenges and clinical outcomes.

Ig-G4 related disease (IgG4RD) is a heterogeneous disorder with multi-organ involvement recognised as a separate entity at the start of this century only. It is currently one of the hottest areas of clinical and translational research across specialties. Thyroid involvement in IgG4RD is rare, believed to occur in less than 4% of cases, may be isolated or may be associated with other organ involvement. As of today Riedel's thyroiditis, fibrosing variant of Hashimoto's thyroiditis, and few patients of Graves' orbitopathy represent the types of IgG4-related thyroid disease (IgG4RTD). This disorder is frequently confused with malignancy due to the intense sclerosis of thyroid resulting in hard texture on palpation compounded by often-associated compressive symptoms. Diagnosis involves establishing high circulating levels of IgG4 > 135 mg/dL, increased serum IgG4 to IgG ratio of > 8%, immunohistochemistry showing dense lymphoplasmacellular inflammatory infiltrate consisting of IgG4-positive plasma cells with storiform fibrosis and obliterative phlebitis, and increased IgG4 positive plasma cell > 10 cells per high-power field when at least three fields are evaluated. Glucocorticoids are the primary form of therapy in IgG4RD. However, their role in IgG4RTD needs to be evaluated. As of today levothyroxine supplementation for resulting hypothyroidism, appropriate management of Graves' disease, and surgical excision of thyroid in case of compressive symptoms remain the primary treatment options. (Endokrynol Pol 2016; 67 (5): 520-524).