If you search on the term ERAP1 allotypes you can come up with some references to Behcet’s disease. Behcet’s Disease (sometimes called Behcet’s Syndrome or Silk Road Disease) is an immune-mediated small-vessel systemic vasculitis that often presents with recurrent mucous membrane ulceration and ocular lesions. It is described as a triple-symptom complex of recurrent oral aphthous (stomatitis) ulcers, genital ulcers, and uveitis. The disease can also involve visceral organs such as the gastrointestinal tract, pulmonary, musculoskeletal, cardiovascular and neurological systems. Skin lesions include erythema-nodosum-like lesions, erythema multiforme-like lesions and Sweet’s Syndrome-like lesions and the inflammatory infiltrating cells are predominantly macrophages.

Behcet’s disease, like the spondyloarthropathies, has a strong contribution to disease by variants of the ERAP1 gene, in fact, the very same ERAP1 allotypes that are linked to AS are seemingly involved in Behcet’s Disease. But whereas AS is associated with the MHC class I molecule HLA-B27, Behcet’s disease is associated with HLA-B51 and HLA-B5. Whilst HLA-B51 is generally below 1% in Caucasians its prevalence can be up to 20% in Turkish populations, for instance.

Why do AS and Behcet’s present so differently – presumably B27 and B51/5 activate and polarise the innate immune system in aberrant, but, different directions. AS is polarised toward the Th17/IL23 axis whilst traditionally BD is regarded as a predominantly Th1-mediated inflammatory disease (with possibly Th17 as well?).




Dx Oct 2006 B27+ undifferentiated spondlyarthropathy (uSpA) with mild sebhorrhoeic dermatitis and mild Inflammatory Bowel Disease (IBD) controlled by NSD since 2007.