USMLE® Step 1 style questions USMLE
A 52-year-old man comes to the ophthalmology clinic because of poor vision for a week. He states that he has also experienced painful ulcers in his mouth during the same period. Medical history is noncontributory. Examination of the mouth shows multiple aphthous ulcers. Visual acuity is 20/60 in both eyes. Examination of the anterior segment is noncontributory, and fundus examination shows white, superficial infiltrates. Which of the following is the most likely diagnosis?
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.