Ankylosing spondylitis involves chronic inflammation of the spine and the sacroiliac joints which are located in the lower back. This chronic inflammation over time can lead to a fusion of the vertebrae. This process is called ankylosis, which leads to loss of mobility of the spine. It also causes pain and stiffness in the back resulting into a bent posture. The most common joints affected are the joints in the buttocks. The lower back, mid-back and the neck is also commonly affected.
It is a systemic rheumatic form of diseases which means it affects other tissues throughout the body along with inflammation of joints away from the spine. The inflammation can lead to pain and tenderness in shoulder blades, ribs, hips, shins, heels and thighs. The hips are the most commonly involved. The knees and shoulders are involved to a lesser extent. Also, the small joints of hands and feet, wrists and ankles are very rarely affected in ankylosing spondylitis.
The persons having this disease are very much likely to have inflammation of the iris of the eye which is called Iritis. Iritis causes the eye to be painful and irritated and sensitive to very bright light. It is also possible though uncommon to have inflammation of the aorta near the heart. This is called as Aortitis.
The causes of ankylosing spondylitis are not clearly known. The disease is said to be triggered by certain types of viral or bacterial infections which activates an immune response which does not stop even after the infection is healed. This immune system then attacks the body’s own tissue thus resulting in disorder.
One of the many causes of ankylosing spondylitis is genetic inheritance. Just as the blood type or hair color is inherited by the child from the parents, the type of tissue is also inherited from them. This tissue typing system is called as the Human Lymphocyte Antigen or HLA system. The HLA – B27 which is a tissue type is present in around six percent of the population in general, but its presence is around 93% in people having ankylosing spondylitis.
Though the HLA – B27 tissue doesn’t cause ankylosing spondylitis, it predisposes those with the B27 tissue type to the disease. Inheriting the tissue does not mean an individual have the chance of having this disease, but they simply get prone to having it. Thus Ankylosing spondylitis tends to run in the family.
There is research going on to identify the agent that causes Ankylosis spondylitis. Researchers are undergoing discussion on whether other genes in the immune system which trigger its development possibly due to interaction with environmental factors.
