Endocrine Abstracts

Introduction: Graves orbitopathy (GO) is the most common extrathyroidal manifestation of autoimmune hyperthyroidism, although it can rarely occur in euthyroid and hypothyroid patients with chronic autoimmune thyroiditis. The eye involvement in GO is frequently bilateral and symmetric. When atypical ocular or incongruent biochemical findings occur, conditions that may mimic GO should be excluded. Immunoglobulin G4 - related disease (IgG4-RD) is a rare, progressive immune-mediated fibrotic disease characterized by tumor-like formations and can affect lacrimal glands, orbits, major salivary glands, pancreas, bile ducts, retroperitoneum, lungs, kidneys, aorta, pachymeninges and thyroid gland.

Case report: A 36 year old woman has been admitted to our hospital due to right unilateral eyeball protrusion, eyelid swelling and redness, chemosis, conjunctival hyperemia and swelling of the right cheek. She had normal thyroid hormone levels (TSH 1.38 mIU/l, reference range 0.27-4.2mIU/l; fT4 19.1 pmol/l, reference range 12-22 pmol/l,). TSH receptor antibodies levels varied from <0.8 to 1.9 IU/l (reference range 0.0-1.8IU/l). Serum IgG4 levels were slightly elevated (IgG4 2.81 mg/dL, reference range 0.03-2.01 mg/dL). An orbital MR imaging showed bilateral increase in the orbital fat volume (predominantly in the right eye), right unilateral proptosis and enlarged two extraocular muscles on the same eye, mimicking GO. The Hertel exophthalmometry implied significant difference in proptosis between eyes (Hertel base 110 mm, right eye 25 mm and left 15 mm). Her past medical history was remarkable for atopy and surgery of the left submandibular salivary gland due to its asymmetrical enlargement with extraction of regional lymph nodes. Revised histopathological findings showed lymphoplasmacytic infiltrate (CD3+ T lymphocytes, activated CD20+ B lymphocytes, rare eosinophils, CD138+ plasmocytes (IgG4/IgG > 40%)) of submandibular salivary gland and lymphadenopathy due to IgG4 infiltrate.

Conclusion: GO and IgG4-RD are conditions with overlapping ocular findings and represent the differential diagnostic challenges, as our case demonstrates. Although clinical findings sometimes suggest GO, IgG4-RD should not be overseen. Biopsy is suggested by some studies for patients who have an unusual clinical course of GO or have clinical characteristics of IgG4-RD.