Bilateral metastatic melanoma to the extraocular-muscles simulating thyroid eye disease

We report a case of bilateral metastatic melanoma to the extraocular muscles that simulated thyroid eye disease. A 71-year-old man presented with bilateral painless axial proptosis, lid retraction and left gaze restriction. Orbital CT scan demonstrated enlargement of the extraocular muscles with tendon sparing, consistent with thyroid eye disease. However, thyroid function tests and antithyroid antibodies were normal. Systemic review including orbital MRI scan determined the correct diagnosis of metastatic melanoma to the orbit. Metastatic melanoma to the orbit can simulate thyroid eye disease.