Idiopathic Orbital Inflammatory Syndrome

Rod Foroozan, MD


January 10, 2008



Idiopathic orbital inflammatory syndrome (IOIS), also known as orbital pseudotumor, is one of the most common acute orbital processes.[1] The pathogenesis of IOIS remains unclear, but the clinical findings have been well-described and may include orbital signs of proptosis, diplopia, decreased vision from optic neuropathy or choroidal folds, and conjunctival injection. Depending on the specific structure involved, IOIS may be further characterized as myositis, dacryoadenitis, or optic perineuritis.

The diagnosis of IOIS is most commonly made on a clinical basis, often in combination with orbital imaging studies; however, in some patients biopsy is required to exclude other orbitopathies that may cause similar symptoms.


Idiopathic Orbital Inflammatory Syndrome: Clinical Features and Outcomes

Swamy BN, McCluskey P, Nemet A, et al
Br J Ophthalmol. 2007;91:1667-1670

Idiopathic Orbital Inflammatory Syndrome: Clinical Features and Outcomes

Swamy BN, McCluskey P, Nemet A, et al
Br J Ophthalmol. 2007;91:1667-1670


The authors of this retrospective case series reviewed the records of 24 patients with biopsy-proven IOIS to characterize the clinical features and outcomes and compare them with the results of orbital biopsy.

Although 98 patients with IOIS were initially included, orbital biopsy was required as an inclusion criterion and that limited the number to 24. Presenting symptoms and signs in the 24 patients included pain (N = 14), swelling or mass effect (N = 19), diplopia (N = 9), proptosis (N = 15), and decreased vision (N = 5). The histopathologic findings included classic changes of IOIS (N = 9), sclerosing changes (N = 13), vasculitic changes (N = 1), and granulomatous changes (N = 1). There did not appear to be a correlation with the clinical findings and the results of orbital biopsy. Treatments included oral steroids in the majority, as well as methotrexate, azathioprine, mycophenalate, and cyclosporine. Recurrence of IOIS occurred in 42% of patients.


IOIS is often a diagnosis that is dependent on the clinical circumstances. In many patients an orbital biopsy is not required. The requirement of biopsy may have caused selection bias in this study. Those who underwent biopsy may have been more likely to have atypical findings or IOIS that was less likely to respond to oral steroids.

Of note, there was no correlation between the histopathologic findings and clinical course in this group of 24 patients. Traditionally, patients with the sclerosing form of IOIS have been thought to have more treatment-resistant disease with a poorer prognosis.[2] This study did not show that the sclerosing form of IOIS had a worse prognosis. It also showed a higher rate of recurrence for the classic type of IOIS.



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