Orbital Lymphoma Masquerading as Euthyroid Orbitopathy.

Thyroid eye disease (TED), also called Graves orbitopathy (GO), is the most common diagnosis of orbital tissue inflammation. It is typically associated with the onset of hyperthyroidism, an autoimmune response to excess amounts of thyroid hormone. However, a visible and palpable lump, strictly unilateral or gross asymmetric eye involvement, non-axial (eccentric) proptosis, a lack of lid retraction or lid lag on downward gaze, or weakened muscle function (suggestive of tendon involvement) are the key features of non-TED mediated ocular involvement, as was found in the case we report here. Orbital lymphoma should always be suspected and excluded in all cases of orbital inflammation. Our patient was diagnosed with mucosa-associated lymphoid tissue (MALT) lymphoma at 27 years of age, two years after the diagnosis of euthyroid ophthalmopathy. This case highlights the need to include space-occupying lesions in the differential diagnosis of proptosis and gaze restrictions, even in younger patients.