Long-term Outcome in 7 Patients With Idiopathic Orbital Myositis.

PURPOSE

Idiopathic orbital myositis, a rare disease of unknown cause, presents a diagnostic puzzle because the diagnosis is based on the exclusion of other diseases. This study aims at elucidating its long-term outcome to answer a clinical question whether idiopathic orbital myositis would be a distinct clinical entity.

METHODS

Retrospective review was made on 7 consecutive patients (6 men and 1 woman) with the age at the initial visit ranging from 33 to 69 years (mean, 45.8 years) who were diagnosed with idiopathic orbital myositis and followed for 5 years or more (mean, 9.2 years) at a referral-based hospital.

RESULTS

Chief complaint at the initial visit was diplopia in 4 patients, blurred vision in 2 patients, and proptosis in 1 patient. On magnetic resonance imaging, 4 patients showed enlargement of a single extraocular muscle on unilateral side while 3 patients showed enlargement of multiple extraocular muscles on unilateral side or bilateral sides. No patient developed systemic diseases or other orbital lesions in the long-term follow-up. All patients at the last visit were free from symptoms, including diplopia, after tapering of prednisolone at the initial dose of 20 to 60 mg daily.

CONCLUSION

Idiopathic orbital myositis had a favorable long-term outcome with corticosteroid administration and appears to be a distinct clinical entity without systemic involvement.