Continuing Medical Education: Spondyloarthropathies.
Edited By: Gregory C. Gardner, M.D.
Last updated Friday, January 07, 2005
IntroductionWhat are the spondyloarthropathies? The spondyloarthropathies are a heterogeneous set of disorders
characterized by axial skeletal involvement and an association with the
HLA B27 antigen. Listed below are the entities included in this group
of disorders.
What is the HLA B27 antigen? The association with the HLA B27 antigen has had a significant impact
on our understanding of these diseases. The HLA B27 antigen is a
so-called class 1 major histocompatibility complex product whose gene
is located on the short arm of the sixth chromosome. The antigen
consists of two chains; an alpha chain made by the gene on the sixth
chromosome, and a B2 microglobulin molecule whose gene is located
elsewhere and stabilizes the alpha chain. All nucleated cells and
platelets contain class 1 molecules. These antigens are important in
the recognition of self by cytotoxic T cells and participate in
immunity to viral infection and also are important in transplantation
rejection. In 1973, it was first recognized that the HLA B27 antigen
was associated with a susceptibility to ankylosing spondylitis. Since
then association with other spondyloarthropathies has been elucidated.
Below is the relative percentages of HLA B27 in patients with these
diseases.Table II. HLA B27 and the Spondyloarthropathies | Spondyloarthropathy | Degree of Association |
|---|
| Ankylosing spondylitis | > 90% |
| Reiter's/reactive arthritis | > 80% |
| Enteropathic spondylitis | 75% |
| Psoriatic spondylitis | 50% |
|
| Normal Population |
|
|---|
| Caucasian | 8% |
| African Americans | 4% |
| Native Americans | 13% |
At least one family study suggests that up to 25% of HLA B27
positive relatives of patients with ankylosing spondylitis may have
signs and symptoms of inflammatory back pain but do not meet full
criteria for ankylosing spondylitis. The utility in ascertaining the
B27 haplotype in individuals with inflammatory back symptoms is that it
might be an impetus to proceed with further evaluation or try second
line anti-inflammatory medications in equivocal cases.
Another important association of the HLA B27 antigen, not listed
above, is in men with lone aortic incompetence in combination with
pacemaker requiring bradycardia.
Recently, the HLA B27 gene was introduced into rats so that there is now an animal model to study these diseases. Surgery for arthritis at the University of Washington If you are interested in making an appointment to discuss this procedure, you can request an appointment using our online referrals website. To request a referral online, please click here. You can also call 206-598-4288 (outside the Seattle area: 800-440-3280) to make an appointment.
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