Analyzing histopathological aspects and cell populations in orbital inflammatory involvement in systemic diseases: A case series from the Rheumatologist's perspective.

Orbital inflammatory disease (OID) comprises approximately 6% of orbital conditions, affecting individuals across all ages. The range of the primary orbital inflammation's differential diagnosis is extensive, encompassing autoimmune disorders such as thyroid diseases, vasculitis, sarcoidosis, connective tissue diseases, immunoglobulin G4-related disease (IgG4-RD), and giant cell myositis, whereas secondary causes span from infections to drug-induced causes. Analyzing histopathological aspects and cell populations could enhance our comprehension of the etiology of orbital inflammatory involvement in systemic diseases such as IgG4-RD. We present a series of four patients from our Rheumatology clinic, each with distinct systemic diseases, illustrating diverse manifestations of OID. This series was conducted to facilitate discussions and diagnoses of challenging cases of OID in a rheumatologic setting. The difficulty in the differential diagnosis arises from the extensive range of structures involved, resulting in a significant variation of clinical manifestations. Furthermore, the lack of definitive diagnostic laboratory tests and, often, histological findings add to the complexity. OID poses diagnostic challenges with variable clinical manifestations and overlapping imaging findings. As a diagnosis of exclusion, a comprehensive evaluation is crucial, often necessitating an orbital biopsy for confirmation. Collaborative efforts among specialists are essential for managing these intricate cases.