Ab1386 Idiopathic Orbital Inflammatory Disease: A Multidisciplinary Approach to Diagnosis, Follow-Up, and Treatment

Background: Idiopathic orbital inflammation (IOI), also known as orbital pseudotumor, is a disease characterized by inflammation of orbital tissues (extraocular muscles, fat, sclera, lacrimal gland, and eyelids) of unknown etiology. It may manifest as an idiopathic entity or concomitantly with various inflammatory diseases. Diagnostic modalities such as orbital MRI and PET/CT, and in cases where feasible, biopsy is employed [1]. Glucocorticoids (GC) are the first-line treatment. The treatment approach for resistant cases is not well-established, but rituximab (RTX) has been reported to be effective [2]. Objectives: In this study, we aimed to examine the clinical findings, therapeutic strategies, and prognosis of patients diagnosed with IOI. Methods: Since 2017, we have been systematically monitoring and treating patients with IOI in collaboration with Department of Ophthalmology, following a standardized plan (Figure 1). As of June 2023, we conducted a retrospective analysis of the clinical characteristics, imaging results, and histopathological findings of a total of 51 patients included in the cohort, based on file records. Results: Fifty-one patients included in the study and the mean age was 45.6±12.9 years. Prior to presenting to our clinic, 43 patients (84.3%) had received oral or parenteral GC, 6 patients (11.8%) had undergone radiotherapy, 7 patients (13.7%) had undergone surgery, and 1 patient had received intra-orbital GC. The predominant symptoms were shown in Table 1. In 49 patients (96.1%), the involvement was unilateral (right: n=24, left: n=25) at the onset of the disease. Orbital MRI was performed in all patients, revealing involvement of extra-orbital muscles, periorbital skin, lacrimal gland, and optic nerve. Among the 50 patients who underwent PET/CT, 15 exhibited FDG uptake in the orbit, consistent with MRI findings. Biopsies were performed in 23 patients (45.1%), demonstrating cell infiltration, predominantly rich in lymphocytes and accompanied by eosinophils. IgG4 was studied in 8 biopsies, and none showed evidence of IgG4-RD. In a total of 11 patients (22%), past or current inflammatory diseases were identified during investigations. Additionally, lymphoma was detected in 3 patients (one simultaneous, two during follow-up). A total of 44 patients (86.3%) received RTX, and 40 patients (78.4%) received MTX. The median number of RTX courses was 2 (range: 1-6). Among the 33 patients who received at least 2 courses of RTX, 32 exhibited clinical improvement. In these 32 patients, 21 experienced complete resolution of symptoms, while 11 had residual symptoms, such as diplopia, ptosis, intermittent mild pain, or mild eyelid swelling, which were considered as sequelae by the ophthalmologist. Concordant findings were observed in orbital MRI and PET/CT in patients who achieved clinical remission. Complete discontinuation of GC treatment was possible in 24 patients (47%) with RTX therapy. In a patient refractory to RTX treatment, cyclophosphamide and then tocilizumab was administered. Conclusion: Despite the histopathological data limitations in our study, it encompasses significant findings. IOI should not be solely regarded as a local inflammation of the eye; rather, it necessitates a comprehensive systemic evaluation involving various disciplines such as ophthalmology, rheumatology, radiology/nuclear medicine, and pathology working collaboratively in a multidisciplinary approach. Differential diagnosis should include conditions such as IgG4-RD, lymphoma, sarcoidosis, and thyroid ophthalmopathy, which could explain the etiology. Orbital MRI and PET imaging should be utilized in the differential diagnosis and follow-up. Considering biopsy feasibility in collaboration with an ophthalmologist, it may be contemplated in cases of resistance, invasion of bony structures, or atypical imaging features. The combined use of GC with RTX and MTX not only reduces the duration of GC use but also diminishes the frequency of exacerbations in this disease associated with relapses. REFERENCES: [1] Mombaerts I, et al. JAMA Ophthalmol. 2017;135(7):769-776. [2] Ng CC, et al. J Ophthalmic Inflamm Infect. 2021;11(1):24. Acknowledgements: NIL. Disclosure of Interests: None declared.