Glaucoma · practice question
Which diagnosis does the tendon involvement most support?
[READINESS SEED] An adult has acute painful proptosis with an enlarged extraocular muscle on imaging; unlike thyroid eye disease, the muscle enlargement extends to and includes the tendon at its insertion. Which diagnosis does the tendon involvement most support?
Show the answer and explanationAnswer and explanation
Answer: A. Idiopathic orbital myositis
Painful proptosis with muscle enlargement that includes the tendon suggests orbital myositis, a form of nonspecific (idiopathic) orbital inflammation; thyroid eye disease classically spares the tendon. But tendon (insertion) involvement occurs in only about half of myositis and is not pathognomonic — also reported in lymphoma, giant-cell myositis, and occasionally thyroid eye disease. Better discriminators are acute pain worse on eye movement and a dramatic steroid response.
Clinical pearl: Nonspecific orbital inflammation is a diagnosis of exclusion; an atypical, recurrent, or steroid-unresponsive case is biopsied to exclude a specific cause such as lymphoma or granulomatosis. Although NSOI is by definition idiopathic, a minority of cases carry an identifiable systemic autoimmune association (Crohn disease, SLE, rheumatoid arthritis, myasthenia gravis, ankylosing spondylitis) yet are still classed as nonspecific.