Endocrine Abstracts

Introduction: First described in 2009, IgG4-related thyroid disease includes several subcategories: Riedel’s thyroiditis, fibrous variant of Hashimoto thyroiditis (FVHT), IgG4-related Hashimoto thyroiditis (HT) and Graves’ disease with elevated IgG4. It is rare, with most cases described in Japan and characterized by increased IgG4 plasma cells at immunostaining.

Case Report: A 59-year-old Caucasian women, without known Asian ancestry, was observed at the endocrinology department due to neck swelling over the previous 4 months. She reported dyspnea at some neck positions, fatigue and constipation. She presented a diffusely enlarged very hard thyroid, with some nodules and reduced mobility. Laboratory evaluation revealed primary hypothyroidism, very elevated titles of anti-thyroglobulin and anti-peroxidase antibodies, elevated erythrocyte sedimentation rate and G immunoglobulins (3400 mg/dl, reference range, RR: 751–1560), elevated IgG4 (267 mg/dl, RR: 4–86) and κ-dominant light chains. There was no monoclonal band; IgA and serum calcium levels were normal. Ultrasound confirmed an enlarged heterogeneous thyroid, with nodules and small calcifications. Cytology was compatible with lymphocytic thyroiditis. The CT scan additionally revealed multiple latero-cervical ganglia, esophageal diversion, airway impression and reduction of the nasopharynx lumen. There was no evidence of malignancy, infection, other autoimmune disorders or non-neck involvement. Euthyroid state was obtained with levothyroxine reposition and total thyroidectomy was performed. Histology revealed a FVHT with elevated IgG4-positive plasma cells and IgG4/IgG ratio. After surgery, serum IgG levels decreased and IgG4 levels became normal.

Discussion: The very hard rapidly enlarging thyroid, short disease duration, high antibody titers, hypothyroidism, diffuse thyroid involvement, no evident extrathyroidal invasion, increased inflammatory parameters, IgG and k dominant profile and elevated IgG4 that normalized after surgery, suggested a fibrous IgG4-HT. Histology and immunostaining confirmed an IgG4-related FVHT. Although very rare in non-Asian countries, it is important to suspect and confirm an IgG4-related thyroid disease, allowing an adequate diagnosis, treatment and follow-up.