- Immune-mediated disorder
- Associated with hyperthyroidism in Graves disease
- Can be seen in hypo or euthyroid individuals
- Orbitopathy often precedes actual thyroid disease
- M:F = 1:4
- 4th to 5th decade
- Most common cause of bilateral or unilateral proptosis
- Deposition of mucopolysaccharides (hyaluronic acid) within extra-ocular muscles
- Fusiform muscle enlargement with sparing of tendon
- Inferior > medial > superior > lateral recti involved
- Isolated lateral rectus involvement (RARE – look for other causes)
- Increase of intra-orbital fat and fat stranding giving a dirty appearance
Tailor, Tina D., et al. “Orbital neoplasms in adults: clinical, radiologic, and pathologic review.” Radiographics 33.6 (2013): 1739-1758.
LeBedis, Christina A., and Osamu Sakai. “Nontraumatic orbital conditions: diagnosis with CT and MR imaging in the emergent setting.” Radiographics 28.6 (2008): 1741-1753.