To describe a case series of patients investigated in internal medicine for an inflammation of the orbit and to clarify the clinical and pathological features of patients with idiopathic orbital inflammatory syndrome (IOIS).Forty patients were consecutively referred by a specialized center where an orbital biopsy was performed in case of accessible lesion. Eleven patients were excluded because of missing data or diagnosis of lymphomas, periorbital xanthogranulomas, or Graves' disease. Patients with systemic disease (SD) or auto-immune disorder (AID) that validated the international criteria, or those having an IOIS in the absence of local or systemic etiology, were included. The clinicopathologic and immunologic characteristics of IOIS patients, their treatment and their evolutionary profiles are reported according to the histological types described by Mombaerts.Of the 29 patients enrolled, eight had a dacryoadenitis revealing a SD/AID, mainly a necrotizing vasculitis, seven patients had a presumed IOIS and 14 an IOIS histologically documented. The presentation of IOIS was dominated by a diffuse involvement of the orbit. Corticosteroids were administered alone or with an immunosuppressant in 57 and 24% of IOIS patients, respectively. The incidence of relapse/resistance was higher than that of remission, particularly in case of presumed IOIS or in its classical form. All four patients with a stage III-IV of Chisholm were relapsing or resistant.A dacryoadenitis may reveal some types of SD/AID. Unlike the severe sialadenitis, the form of sclerosing IOIS may not be a factor associated with relapse or resistance.