[Inferior rectus muscle metastasis as a presenting sign of renal cell carcinoma: case report].

Proptosis and diplopia due to enlargement of extraocular muscles represent important presenting signs of many orbital disorders. Although dysthyroid ophthalmopathy is the most common cause of enlargement of extraocular muscles, the differential diagnosis is extensive. We report a patient with a 3-month history of diplopia and unilateral proptosis and a markedly enlarged inferior rectus muscle on imaging studies. A biopsy of the lesion followed by systemic evaluation established the diagnosis of metastatic renal cell carcinoma. There are few cases of metastatic tumors to the extraocular muscles reported in the literature and thus our objective is to report a new case, review the literature and reiterate the inclusion of this disorder in the differential diagnosis of enlargement of the extraocular muscles.