Ankylosing Spondylitis

Description

 Common (More than 200,000 cases per year in US)

 Treatments can help manage condition, no known cure

 Often requires lab test or imaging

 More common in males

 Family history may increase likelihood

Ankylosing spondylitis (AS) is a type of arthritis in which there is a long-term inflammation of the joints of the spine. Typically the joints where the spine joins the pelvis are also affected. Occasionally other joints such as the shoulders or hips are involved. Eye and bowel problems may also occur. Back pain is a characteristic symptom of AS, and it often comes and goes. Stiffness of the affected joints generally worsens over time.

Also known as: bechterew’s disease, Ankylosing Spondylitis (AS) is one of the major forms of chronic inflammatory arthritis and is the prototypical example of the spondyloarthropathies, a group of chronic autoimmune joint diseases.

Ankylosing Spondylitis has a global distribution, though rarer in Africans. It is characterized by arthritis affecting the spine and pelvis. It specifically involves the sacroiliac joint and initially causes pain and reversible stiffness (stiffness in the mornings that goes away later in the day with exercise) but leads to progressive joint fusion with irreversible stiffness and deformity in a number of cases.

Clinical Utility

There is a strong association with the HLA class I molecule HLA-B27, found in upwards of 90% of patients. Association of AS to B27 is amongst the strongest genetic associations with a common disease, although the mechanism of action remains uncertain.  The strong association of HLA-B27 with AS makes B27 testing a useful component of the diagnostic work up which includes a physical examination, use of X-rays, MRI, and a check for family history of AS. The value of B27 testing is that it allows a presumptive diagnosis and early treatment in patients showing some of the symptoms and before the damage to joints would already have happened.

Scientific References

• Evans DM et al. Interaction between ERAP1 and HLA-B27 in ankylosing spondylitis implicates peptide handling in the mechanism for HLA-B27 in disease susceptibility. Nat Genet. 2011; 43:761.
• Granfors K et al. The cutting edge of spondylarthropathy research in the millennium. Arthritis Rheum. 2002; 46:606.
• Reveille JD. Genetics of spondyloarthritis–beyond the MHC. Nat Rev Rheumatol. 2012; 8:296.
• Reveille JD. Recent studies on the genetic basis of ankylosing spondylitis. Curr Rheumatol Rep. 2009; 11:340.
• Uchanska-Ziegler B et al. Structural and dynamic features of HLA-B27 subtypes. Curr Opin Rheumatol. 2013; 25:411.