[Idiopathic orbital inflammatory syndrome: Report of 24 cases].

Background: Idiopathic orbital inflammatory syndrome (IOIS) is an inflammatory condition of unknown etiology. The inflammation may affect all the structures within the orbit (anterior, diffuse, apical, myositic, dacryoadenitis) and corresponds to uniquely orbital inflammation without an identifiable local cause or systemic disease. The goal of this study is to describe the clinical and radiographic characteristics of IOIS and discuss the role of orbital biopsy in this condition.

Patients And Methods: This is a retrospective review of the charts of 24 patients diagnosed with IOIS at Fattouma Bourguiba hospital, Monastir, Tunisia, from January 2007 to December 2015. This study included all patients with IOIS and a minimum follow-up of six months. All patients had a complete ophthalmological examination and orbital and head CT scan and/or MRI. A work-up was performed in all cases to rule out local causes and systemic disease. Only 11 patients underwent biopsy. The diagnosis of the clinical entity IOIS was made according to the Rootman criteria. Oral steroids were the first line therapy. A bolus of intravenous methylprednisolone was administered first in vision-threatening cases. Response to treatment was defined as disappearance of signs and symptoms of IOIS.

Results: Orbital pain was the most common symptom (62.5%), followed by proptosis and decreased vision (37.5% each). Best-corrected visual acuity (BCVA) was greater than 5/10 in 70.7% of patients. Lacrimal gland enlargement was observed in 3 patients. Oculomotor disorders were present in 70% of cases and 20.8% of patients had compressive optic neuropathy. Orbital imaging showed, in most cases, oculomotor muscle inflammation (87.5%) involving particularly the superior rectus muscle (54.2%) and inflammation of orbital fat (66.7%). Fifty percent had myositic inflammation. Biopsy was performed in 11 patients, showing nonspecific inflammation (n=10) and the sclerosing form (n=1). A total of 83.3% of patients received oral corticosteroids for a mean duration of 5.5 months.

Conclusion: IOIS is a diagnosis of exclusion, based on history, clinical course, response to steroid therapy, laboratory tests, or even biopsy in selected cases. Orbital imaging provides valuable clues for diagnosis of IOIS and for identification of affected structures. Prolonged steroid therapy is necessary as IOIS classically responds to steroids; nevertheless, partial recovery or relapses often occur.