Two cases of orbital myositis with monoclonal gammopathy of undetermined significance

PURPOSE: We report two cases of idiopathic orbital myositis with monoclonal gammopathy. CASE: Case one was a 47-year-old man, who had bilateral swelling of the extraocular muscles and impairment of the left optic nerve. Case two was a 27-year-old woman, who had bilateral proptosis. An immunological test showed that both patients had monoclonal gammopathy, and they were diagnosed as having monoclonal gammopathy of undetermined significance(MGUS). RESULTS: In case one, the patient achieved remission with steroid pulse therapy followed by administration of high doses of a steroid. In case two, because of repeated recurrence, the patient was treated with steroid pulse therapy and then radiation therapy to achieve final remission. CONCLUSION: We need to pay attention in the diagnosis of orbital myositis to distinguish MGUS. Such patients have an atypical clinical course and are resistant to ordinary steroid therapy.