SNP Shot: Genomic Insights

Ankylosing spondylitis (AS) is a painful, long-term form of arthritis that causes inflammation in the joints, primarily affecting the spine. This chronic inflammatory arthritis usually starts between the ages of 15 and 30. The most common initial symptoms are persistent back pain and stiffness. Notably, the pain worsens with rest or inactivity, but tends to improve with physical activity or exercise.

The pain associated with AS stems from inflammation in the sacroiliac joints, which are located where the pelvic bones (ilia) meet the base of the spine (sacrum). This inflammation is called sacroiliitis. Over time, the inflammation spreads to the joints between the vertebrae, affecting the entire spine and causing spondylitis. As the condition progresses, the spine's flexibility decreases as the vertebrae gradually fuse together, a process called ankylosis. These fused bones are more susceptible to fractures.

AS can also affect other joints, such as the shoulders, hips, and, less frequently, the knees. As the disease advances, it can impact the joints connecting the spine and ribs, restricting chest movement and making deep breathing difficult.

In over 30% of cases, AS affects the eyes, leading to episodes of acute iritis, an inflammation of the eye. Typically, acute iritis affects one eye at a time, causing pain and increased sensitivity to light (photophobia). In rare instances, AS can lead to serious complications involving the heart, lungs, and nervous system. Between 6% and 10% of individuals with AS also have other inflammatory conditions, such as psoriasis (affecting the skin) or ulcerative colitis or Crohn's disease (both affecting the digestive system).

Inheritance:

While AS can occur in multiple family members, it's not solely determined by genetics. A combination of genetic and environmental factors likely contributes to the risk of developing AS. Therefore, inheriting a gene associated with AS doesn't guarantee the development of the condition, even in families with multiple affected members. Research indicates that approximately 75% of children who inherit the HLA-B27 gene from a parent with AS do not develop the disorder.