Endocrine Abstracts (2013) 32 P1022 | DOI: 10.1530/endoabs.32.P1022

IgG4-related Hashimoto's thyroiditis: an emerging variant of a well known disease

Henrique Luiz, Diogo Gonçalves, Bernardo Pereira, Tiago da Silva, Andreia Veloza, Catarina Matos, Isabel Manita, Maria Cordeiro, Luísa Raimundo, Ana Oliveira, Maria Brito & Jorge Portugal

Garcia de Orta Hospital, Almada, Portugal.

Introduction: IgG4-related Hashimoto’s thyroiditis (HT) is a very recently reported entity, characterized by thyroid inflammation rich in IgG4-positive plasma cells associated with marked fibrosis. It may be part of the systemic IgG4-related sclerosing disease and is associated with younger age, lower female:male ratio, higher levels of thyroid autoantibodies, low echogenicity on ultrasound (US), rapid progress requiring surgery and more subclinical hypothyroidism, when compared with non-IgG4 HT.

Case report: A 56-year-old man presented with a 4-month history of progressive neck swelling, dysphagia, and weight loss of 7 kg. Cervical palpation identified an enlarged, hard and painless thyroid gland. Laboratory testing revealed: increased ESR, 81 mm/h (<31) and CRP, 8.2 mg/dl (<1), elevated TSH, 19 mIU/l (0.1–4), normal free T4, 0.99 ng/dl (0.93–1.7) and very high levels of anti-Tg, >4000 IU/ml (<40) and anti-TPO, >600 IU/ml (<35). US demonstrated an enlarged and heterogeneous thyroid gland, with a substernal component, both lobes with maximal dimension >10 cm and two hypoechoic nodules with 3.2 and 2.2 cm located on the isthmus and right lobe, respectively. US-guided fine needle aspiration cytology was performed and the material removed from both nodules was consistent with lymphocytic thyroiditis. The patient was submitted to total thyroidectomy with no surgical complications. Histological findings showed lymphoplasmacytic infiltration, lymphoid follicles with germinal centers and marked fibrosis limited within the thyroid capsule; an increased number of IgG4-positive plasma cells was found by immunohistochemistry. One month after surgery, serum IgG4 concentration was high-normal, 165 mg/dl (3–201). Symptoms relief and reduction in laboratory inflammatory parameters were noticed. Thyroid function was controlled with levothyroxine.

Conclusions: We report a typical case of IgG4-related HT. The presentation form suggested the diagnosis, which was confirmed based on histological data. Our case highlights this new variant of the well known HT, and helps physicians in recognizing its main clinical features.