What is a key characteristic of ankylosing spondylitis?

A key characteristic of ankylosing spondylitis is the progressive fusion of the spine. This condition primarily affects the axial skeleton, leading to chronic inflammation of the vertebrae and the sacroiliac joints. Over time, this inflammation can result in the formation of bone in the areas where ligaments attach to bones, causing the vertebrae to fuse together. This fusion restricts spinal mobility, often leading to a characteristic stooped posture known as "bamboo spine."

The progressive nature of this fusion is crucial in identifying the disease and understanding its long-term impact on the patient's mobility and quality of life. Early diagnosis and management can help to alleviate symptoms and slow the progression of the disease, but the hallmark feature remains the eventual fusion of the spinal column.