[Etiological investigation of inflammatory orbital disease in patients seen in internal medicine].

Inflammatory orbital diseases are characterized by inflammation that may involve any structure of the orbit including lacrimal gland, and may represent the manifestation of numerous disorders. Thereby, they are grouped under the term orbital inflammatory syndrome (OIS). A distinction is made between primary OIS of purely inflammatory etiology, whether identified or not - the latter being considered idiopathic orbital inflammatory syndrome (IOIS) - and secondary OIS resulting from a local or systemic cause such as infection, neoplasia, or even iatrogenic conditions. In this review, we describe the autoimmune/systemic diseases most frequently revealed or heralded by OIS, as well as the orbital manifestations that characterize them. Thus, in the presence of bilateral dacryoadenitis, IgG4-related disease and sarcoidosis should be investigated first as granulomatosis with polyangiitis in cases of intraorbital mass. Furthermore, we propose an update of our diagnostic algorithm based on topographic information provided by orbital imaging. When systemic investigations fail to identify an underlying disease (in more than 50% of cases), orbital biopsy should be considered in order to distinguish nonspecific inflammation from lymphoma. In cases of isolated myositis or posterior orbital masses for which biopsy may entail deleterious complications, diffusion-weighted MRI analysis of orbital lesions can help differentiate purely inflammatory lesions from lymphoma. When the diagnostic work-up fails, a therapeutic trial of corticosteroids may still be considered, while keeping in mind corticosteroids have sometimes a beneficial effect on lymphomas. In future, artificial intelligence-based analysis of biomarkers generated through omics technologies should contribute significantly to differentiating orbital lymphomas from IOIS.