USMLE® Step 1 style questions USMLE
A 27-year-old man comes to the office due to 6 days of eye redness and pain in both eyes. Medical history is significant for recurrent painful oral ulcers and ankylosing spondylitis. He currently takes aspirin and sulfasalazine. The patient is in a monogamous relationship but is unsure sure if his partner is monogamous. The patient immigrated from Turkey when he was a child. Temperature is 36.5°C (97.7°F), pulse is 98/min, respirations are 14/min, and blood pressure is 120/70 mmHg. Physical examination shows warm and tender nodules over bilateral shins as well as his left ankle, as shown in the image below:
Reproduced from: Wikipedia
On ophthalmological examination, decreased visual acuity, conjunctival redness, and hypopyon are noted bilaterally. Genital exam reveals an incipient genital ulceration over the scrotal raphe. Laboratory studies show elevated erythrocyte sedimentation rate. This patient most likely has which of the following conditions?
Content Reviewers:Rishi Desai, MD, MPH
Among the family of disorders that cause vasculitis, Behcet’s is fairly unique because it causes inflammation in blood vessels of all sizes—small, medium, and large ones—on both the arterial and venous side of the circulation.
The underlying cause of Behcet’s is unknown, but there are a number of clues.
The biggest clue is that the human leukocyte antigen, or HLA, genes seem to play a role, and this is based on the fact that having a specific type—the HLA-B51 type—predisposes individuals to having Behcet disease.
HLA genes encode proteins found on the surface of immune cells, and play a key role in regulation of those cells, and since the disease is a result of an autoimmune process, it makes sense that the HLA-B51 proteins could be involved.
Another, clue is that an individual’s response to viral and bacterial infections might be involved.
And this is an example of molecular mimicry where an antibody to a foreign pathogen starts to cross-react and damage the person’s own tissue.
Individuals with Behcet’s also seem to have a weakened innate immune system, a higher proportion of autoreactive T cells, and activated neutrophils which destroy healthy tissue, as well as altered levels of T helper cells and cytokines.
In summary, these clues span genetic and environmental factors as well as both the innate and adaptive immune system.
Sometimes the inflammation can get so severe that the tissue around the vessel starts to die off completely.
These changes make the endothelial lining more likely to develop blood clots or aneurysms.
Having said that, most people initially present with recurrent oral ulcers.
Relative to aphthous ulcers, the oral ulcers of Behcet disease can be larger, more painful, and take a few weeks to heal, sometimes recurring before a previous round of ulcers has resolved, which means that they can be almost continuously present.