Ab0883 idiopathic Ophthalmic Myositis: Clinical Presentation, Therapeutic Approach and Imaging Differentiation From Graves Ophthalmopathy

Abstract

BackgroundIdiopathic ophthalmic myositis (IOM) represents a rare autoimmune ophthalmoplegia of unknown etiology, that may mimic predominantly Graves’ ophthalmopathy (GO). IOM is characterized by pronounced inflammatory infiltration of extraocular muscles leading to fibrosis and eye-threatening complications, if remains untreated [1,2]. The rarity and clinical heterogeneity of the disease pose diagnostic and therapeutic challenges.ObjectivesTo describe the clinical phenotype, therapeutic interventions and clinical course of IOM and to define the distinct imaging features that differentiate IOM from GO.MethodsThis is a single-center, retrospective, observational study of 14 consecutive patients with IOM followed-up between 2017 and 2022. Cumulative clinical, laboratory and imaging data from the medical records until last follow-up were analyzed. The detailed orbital magnetic resonance (MRI) findings of 11 IOM patients were compared to those of 16 age- and sex-matched GO patients.ResultsIOM patients studied (men: 9/14, median age at disease onset: 46 years, median follow-up time: 15.5 months), presented subacute clinical course in 57%, whereas most common clinical manifestations were unilateral exophthalmos (79%), diplopia (71%), eyelid drop and/or swelling (50%). Extraocular muscle inflammation most commonly involved horizontal recti (median number of affected muscles: 2) and predominantly caused restrictive motility disturbance (71%). Anemia of chronic disease occurred in 36% of patients, however, erythrocyte sedimentation rate and c-reactive protein levels were found within normal limits. Myositis specific or other autoantibodies were not detected. Orbital MRI assessments revealed significantly more frequent occurrence of intraconal/extraconal fat edema (in at least one eye) in IOM patients (64.0%), compared to GO patients (25.0%, p-value 0.01). In addition, the abnormal contrast enhancement in extraocular muscles was present in 91.0% and 75.0% of IOM and GO patients, respectively, whereas tendon involvement was observed exclusively in IOM patients (18.2%). In all patients, the mainstay of therapy was steroids. IOM patients were treated with various combinations of corticosteroids and c-DMRD/b-DMRD (methotrexate, mycophenolate-mofetil, azathioprine, rituximab, tocilizumab), whereas GO patients mainly received corticosteroids with/or without tocilizumab.ConclusionIOM is a potentially severe organ-specific disease with heterogeneous clinical presentation. Early diagnosis and aggressive immunosuppressive treatment are required to prevent permanent eye-threatening complications. IOM should be considered in the differential diagnosis of exophthalmos, while MRI-imaging may help in differentiating IOM from GO. Studies are underway to delineate tissue-specific alterations of the inflamed extraocular muscles and involving larger series of patients.References[1]McNab A. Orbital Myositis: A Comprehensive Review and Reclassification. Ophthalmic Plast Reconstr Surg. 2020[2]Montagnese F., Wenninger S. & Schoser B. “Orbiting around” the orbital myositis: clinical features, differential diagnosis and therapy.J Neurol2016.Acknowledgements:NIL.Disclosure of InterestsNone Declared.