Idiopathic Orbital Inflammation (IOI) may occur as a diffuse myositis (myositic) or as inflammation without diffuse myositis (nonmyositic).
The age of onset is typically from 10 to 60 years of age.
Features of myositic IOI:
(1) extraocular muscle enlargement
(2) contrast-enhanced
(3) orbital pain
(4) painful eye movement
(5) enlarged muscle tendon
(6) acute or subacute onset
(7) limited eye movement
(8) unilateral
(9) intact orbital bone
(10) no history of thyroid disease
(11) supraorbital and infraorbital nerve of normal size
(12) adjacent paranasal sinuses are normal
(13) compatible pathologic findings
(14) dramatic improvement after administration of systemic steroids (prednisolone 1 mg/kg/d).
