Not All Orbitopathy Is Graves': Discussion of Cases and Review of Literature

Abstract

Introduction: Graves' orbitopathy is the extra thyroidal manifestation of Graves' disease and the most common cause of exophthalmos. It is also known as thyroid-associated orbitopathy (TAO) as it occasionally occurs in euthyroid or hypothyroid patients with chronic thyroiditis. 5% of patients with Graves' orbitopathy can be euthyroid or hypothyroid as they have low titers of anti-thyrotropin-receptor antibodies, which are difficult to detect in some assays. Orbitopathy has also been seen in a small percentage of patients with Hashimotos thyroiditis. The eye involvement in Graves' is frequently bilateral and symmetric. These patients pose few diagnostic difficulties when the ocular findings occur concomitantly with the thyroid disease. However, when unilateral and asymmetric ocular findings occur with normal or mildly abnormal thyroid function tests, alternate etiologies should also be pursued. We aim to discuss some conditions like sarcoidosis, lymphoma, orbital pseudotumor, and orbital malignancy that mimic TAO.

Cases: Three patients were referred to us with concern for Graves' orbitopathy. After further work-up, we diagnosed the first patient with specific orbital myositis from sarcoidosis. Our second patient had CD10-positive B-cell lymphoma. Our third patient had orbitopathy likely secondary to Hashimotos or orbital pseudotumor.

Conclusion: Our cases and discussion describe some other conditions that clinically mimic TAO and the importance of pursuing further work-up for accurate diagnosis when presentation of orbitopathy is atypical.

Keywords: Graves’ orbitopathy; differential of thyroid-associated orbitopathy; orbital lymphoma; orbitopathy; sarcoid orbitopathy.

Figure 1

Case 1. Diffuse enlargement and enhancement of muscle bellies and anterior tendinous insertions of bilateral extraocular muscle on coronal and axial T2 (A,B) and fat suppressed post contrast T1 (C,D) orbital images. Involvement of the tendons and lateral rectus muscle makes Graves’ orbitopathy less likely. Additional findings, which favored the diagnosis of sarcoidosis included nodular leptomeningeal enhancement (F,G) with thickening of the pituitary stalk (E).

Figure 2

Case 2. T1 hypointense and T2 hyperintense mildly enhancing mass in the left superior rectus muscle seen on coronal T1 (A), fat saturated T2 (B), and post contrast fat saturated T1 (C) images of the orbits. Solitary muscle involvement especially of the superior rectus makes thyroid orbitopathy an unlikely etiology.

Figure 3

Case 3. Coronal T2W MRI images showing enlargement of the right inferior rectus muscle [arrow in (A)] with surrounding fat stranding, features similar to thyroid-associated orbitopathy (TAO). Focal sparing of the anterior tendinous insertion [arrow in (B)] is another common finding of TAO.