We have already seen in the previous posts that HLA-B27 is the
most common gene associated with Ankylosing spondylitis (AS).
However, HLA-B27 does not seem to be the only gene associated
with AS. Strong indicators of this fact include- 1. AS can occur
in individuals who do not carry HLA-B27 gene. 2. Amongst the
HLA-B 27 individuals, only about 1-5% individuals develop AS. 3.
HLA-B27 positive relatives of AS patients have a risk of
developing AS that is 5.6 to 15 times that of HLA-B27 positive
individuals in general population. This would mean that there
are other non HLA-B27 familial genetic factors involved in
causation of AS. There has been some major work by the Wellcome
trust case Control Consortium & Australo-Anglo-American
Spondyloarthritis Consortium to look into the genetics of AS.
These (& other) studies have revealed that there are other genes
& genetic loci responsible for Ankylosing spondylitis as well—
1. HLA-B60 seen in HLA-B27 positive as well as negative AS
patients. 2. HLA-B 39 seen in HLA-B2