B27 homozygosity and ankylosing spondylitis

Area of Science:

• Immunogenetics
• Rheumatology
• Genetics

Background:

• Ankylosing spondylitis (AS) is strongly associated with the HLA-B27 gene.
• The role of B27 homozygosity in AS pathogenesis and risk remains unclear.

Purpose of the Study:

• To investigate the frequency of B27 homozygosity in AS patients.
• To determine if B27 homozygosity increases the risk for developing AS.
• To explore the potential influence of B27 homozygosity on AS disease severity.

Main Methods:

• Determined B27 homozygosity frequency in 100 B27-positive AS patients.
• Compared observed homozygosity frequency with expected frequency in blood donors.
• Studied AS prevalence in homozygous versus heterozygous family members of AS patients.

Main Results:

• Six of 100 AS patients (6%) were B27 homozygous.
• Observed homozygosity frequency was not significantly different from expected (2.3%).
• No difference in AS prevalence was found between homozygous and heterozygous family members.

Conclusions:

• B27 homozygosity does not appear to increase the risk of developing ankylosing spondylitis.
• B27 homozygosity may be associated with moderate to severe AS, suggesting a role in disease severity rather than susceptibility.