The HLA-B27 genotype is a variant of the human leukocyte antigen gene family that is strongly associated with the degenerative disease ankylosing spondylitis and other inflammatory diseases, according to the scientific journal Rheumatology. Research indicates that this gene variant produces proteins that may increase the tendency of the body's immune system to attack connective tissues and produce the inflammation symptoms common to ankylosing spondylitis and other diseases associated with HLA-B27.
Ankylosing spondylitis is an inflammatory condition that can result in the vertebrae of the spinal column fusing together, writes Mayo Clinic. This fusion reduces flexibility and mobility of affected individuals and can also cause considerable pain. Cartilage and joint tissues at the intersection of the hips and spinal column, in the knees and shoulders, and between the ribs and the sternum may also be affected by this disease. Ankylosing spondylitis can also affect the eyes and cause vision loss, though this is not as common as joint-related symptoms.
The HLA-B27 genotype is also associated with other inflammatory diseases in addition to ankylosing spondylitis, reports Rheumatology, though the association with spondylitis is the strongest. Other diseases associated with HLA-B27 include reactive arthritis that develops after infections and sacroiliitis associated with psoriasis or irritable bowel syndrome. However, the HLA-27B variant is relatively common in the population and is likely insufficient to cause these diseases without the involvement of other risk factors.