Ankylosing spondylitis (AS) is a chronic autoimmune form of arthritis that causes inflammation, pain and stiffness in the spine and sacroiliac joints (just above your tailbone). Inflammation in these areas can cause some of the vertebrae in your spine to fuse together. In severe cases, you cannot lift your head high enough to see ahead of you. AS can also damage organs such as the heart and kidneys. AS affects men more than women and typically begins in early adulthood. There is no cure for AS but early diagnosis and treatment can ease pain and symptoms.