Endocrine Abstracts

Introduction: Immunoglobulin G4 related disease (IgG4-RD) is an immune-mediated fibro-inflammatory condition and is a widely recognised multi-organ system disease. The prevalence of IgG4-RD is 6/100 000, but it is likely to be underestimated. IgG4-RD is characterised by elevated serum levels of IgG4 and IgG4-positive lymphoplasmacytic infiltrative lesions in the body. Recent reports suggest disease involvement in various organs including thyroid and orbital tissues. Thyroid disease described in IgG4-RD encompasses Hashimoto’s thyroiditis, fibrosing variant of Hashimoto’s thyroiditis, Reidel’s thyroiditis and Graves disease.

Case presentation: A 47-year-old lady was referred to the Endocrine clinic with primary hypothyroidism [TSH 78.2 mIU/l (0.27–4.20), fT4 1.2 pmol/l (12–22) and fT3 < 0.4 pmol/l (3.1–6.8)].There is a family history of thyroid disorder. She had strongly positive TPOAb (>500 IU/ml) and TgAb (>5000 IU/ml), and was diagnosed with Hashimoto’s thyroiditis. Thyroxine replacement was started. Initial examination revealed a small diffuse goitre with bilateral periorbital swelling on the upper lids and mild proptosis. A left thyroid nodule was palpable in subsequent visit and USS neck with FNAC was performed. Both thyroid lobes were hypoechoic and lobular in appearance with a 1.1 cm × 0.7 cm hypoechoic nodule in the medial left thyroid. FNAC of the thyroid nodule showed lymphocytic infiltration consistent with Hashimoto’s thyroiditis. Serum IgG4 level was markedly elevated (2230 mg/dl; 2.4–121). She was referred to the Rheumatology clinic with suspected IgG4-RD. MRI orbit confirmed bilateral lacrimal gland enlargement. Biopsy of the lacrimal gland showed marked inflammatory cell infiltrates including lymphocytes and plasma cells. Immunostaining revealed increased numbers of IgG4 positive plasma cells among infiltrating lymphocytes. The findings were consistent with IgG4 associated ophthalmic disease. Prednisolone was started following a diagnosis of IgG4-RD.

Discussion: Our patient has Hashimoto’s thyroiditis with underlying IgG4-RD. Hashimoto’s thyroiditiscan be further subclassified into IgG4-thyroiditis and non-IgG4 thyroiditis. Thyroid nodule FNAC could not confirm the subtype of Hashimoto’s thyroiditis in our patient. However, she has significantly elevated TPO-Ab and Tg-Ab and hypoechoic thyroid gland on ultrasonography. These features on a background of IgG4-RD suggest our patient has IgG4-thyroiditis. Bilateral lacrimal gland enlargement is in keeping with IgG4-RD manifestation in the eye which usually causes painless swelling of the lacrimal glands with chronic lid swelling and proptosis. Diagnosis of IgG4-RD can be challenging as it is uncommon and requires a combination of clinical features, serological confirmation and histological evidence with IgG4 immunostaining. The first line of treatment is usually glucocorticoid therapy. Prompt diagnosis and treatment can reduce progression of the disease.