October 24, 2010

USMLE 2 Question 20

A 30 year old man presents with bilateral eye pain. He is thought to have conjunctivitis and is given antibiotic eye drops but the pain persists and recurs with blurriness, redness and photophobia. A slit lamp examination reveals tiny floating particles in the anterior chamber between the cornea iris and tiny dots on the back layer of the cornea. The pupil appeared stuck to the lens behind

a) Ankylosing spondylitis
b) Reactive arthritis
c) Psoriatic arthropathy
d) Pyrophosphate arthropathy
e) Haemochromatosis

The correct answer is A

The eye is made of 3 coats. The middle coat is called the uvea. It consists of the iris in the front, the ciliary body a little further back (pars plicata + pars plana,) and the choroid at the back behind the retina.

Uveitis is a broad term referring to inflammation of any of the components of the uvea.

THE SLIT LAMP MICROSCOPE: (1) In the anterior chamber between the cornea and iris - CELLS which are tiny floating particles, and FLARE which is a visible beam of light. (2) On the back layer of the cornea, tiny dots called Keratic Precipitates (KP's) which are adherent inflammatory cells. (3) The pupil can get stuck to the lens behind causing adhesions called POSTERIOR SYNECHIAE.

This patient's recurrent anterior uveitis represents an HLA-B27-associated primary spondyloarthropathy. His systemic signs and symptoms could be due to HLA-B27-associated, non-specific disease processes (undifferentiated or unclassifiable spondyloarthropathy). Or, they may not be related to the HLA-B27 antigen at all.

There is a strong relationship between acute anterior uveitis and HLA-B27. Studies show that more than 50 percent of cases of acute anterior uveitis are associated with the HLA-B27 antigen.

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