Idiopathic Orbital Inflammation

  • Autoimmune inflammation of orbital soft tissues ("idiopathic orbital inflammation," abbreviated IOI)
  • Inflammation often seated in extraocular muscles and then also called "orbital myositis"
  • Diagnosis based on clinical features, imaging, and sometimes biopsy
  • Usually improves with systemic or orbital injection of corticosteroids, but...
  • May recur
  • Periocular pain, lid swelling, eye surface vessel hyperemia, diplopia
  • Usually unilateral
  • Onset subacute
  • Orbital imaging may show proptosis, lid swelling, vascular congestion, extraocular muscle or lacrimal gland enlargement, dural and periosteal enhancement
  • Orbital inflammation caused by granulomatous polyangiitis, other vasculitides, connective tissue diseases, sarcoidosis, fungal infection, all of which require non-orbital findings or biopsy for diagnosis
  • Graves disease, but IOI has more rapid onset, more pain, is more often unilateral, and has no lid retraction or lag
  • Bacterial orbital cellulitis, but IOI has slower onset, and is more likely to show extraocular muscle or lacrimal gland enlargement
  • Orbital tumor, but imaging in IOI does not show masses except within extraocular muscles or lacrimal gland
  • Cavernous sinus arteriovenous fistula, but that shows enlarged superior ophthalmic vein on imaging
  • Refer patient urgently for clinical and imaging assessment
  • Prompt orbital imaging (CT or MRI) necessary for diagnosis
  • If imaging suggests IOI, next step is CT of chest, abdomen, pelvis to rule out other sites of inflammation or tumor
  • If orbit only site of disease, patient will be treated with corticosteroids, with expected improvement within days
  • If there is no improvement or recurrence upon tapering steroids, orbital biopsy will be considered to exclude non-idiopathic inflammation, neoplasm
  • IOI may resolve without treatment or after one episode of treatment, but...
  • May also be recurrent, requiring chronic immunomodulatory treatment, and...
  • Leaving behind scarred tissue that causes permanent diplopia and even vision loss