Ankylosing spondylitis is also a systemic rheumatic disease. Therefore, it can cause inflammation in other joints away from the spine, as well as other organs, such as the eyes, heart, lungs, and kidneys. Ankylosing spondylitis shares many features with several other arthritis conditions, such as psoriatic arthritis, reactive arthritis, and arthritis associated with Crohn's disease and ulcerative colitis. Each of these arthritic conditions can cause disease and inflammation in the spine, other joints, eyes, skin, mouth, and various organs. In view of their similarities and tendency to cause inflammation of the spine, these conditions are collectively referred to as "spondyloarthropathies." For more information, please see the Psoriatic Arthritis, Reactive Arthritis, Crohn's Disease and Ulcerative Colitis articles of MedicineNet.com.

 

Ankylosing spondylitis is 2-3 times more common in males than in females. In women, joints away from the spine are more frequently affected than in men. Ankylosing spondylitis affects all age groups, including children. The most common age of onset of symptoms is in the second and third decades of life.

What causes ankylosing spondylitis?

The tendency for developing ankylosing spondylitis is believed to be genetically inherited, and the majority (90%) of patients with ankylosing spondylitis are born with the HLA-B27 gene. Blood tests have been developed to detect the HLA-B27 gene marker, and have furthered our understanding of the relationship between HLA-B27 and ankylosing spondylitis. The HLA-B27 gene appears only to increase the tendency of developing ankylosing spondylitis, while some additional factor(s), perhaps environmental, are necessary for the disease to appear or become expressed. For example, while 7% of the United States population have the HLA-B27 gene, only 1% of the population actually have the disease ankylosing spondylitis. In Northern Scandinavia (Lapland), 1.8% of the population have ankylosing spondylitis while 24% of the general population have the HLA-B27 gene. Even among HLA-B27 positive individuals, the risk of developing ankylosing spondylitis appears to be further related to heredity. In HLA-B27 positive individuals who have relatives with the disease, their risk of developing ankylosing spondylitis is 12% (6 times greater than for those whose relatives do not have ankylosing spondylitis).
How inflammation occurs and persists in different organs in ankylosing spondylitis is a subject of active research. The initial inflammation may be a result of an activation of body's immune system by a bacterial infection. Once activated, the body's immune system becomes unable to turn itself off, even though the initial bacterial infection may have long subsided. Chronic tissue inflammation resulting from the continued activation of the body's own immune system in the absence of active infection is the hallmark of an autoimmune disease.

What are the symptoms of ankylosing spondylitis?

The symptoms of ankylosing spondylitis are related to inflammation of the spine, joints, and other organs. Inflammation of the spine causes pain and stiffness in the low back, upper buttock area, neck, and the remainder of the spine. The onset of pain and stiffness is usually gradual and progressively worsens over months. Occasionally, the onset is rapid and intense. The symptoms of pain and stiffness are often worse in the morning, or after prolonged periods of inactivity. The pain and stiffness are often eased by motion, heat and a warm shower in the morning. Because ankylosing spondylitis often affects patients in adolescence, the onset of low back pain is sometimes incorrectly attributed to athletic injuries in younger patients.

Patients who have chronic, severe inflammation of the spine can develop a complete bony fusion of the spine (ankylosis). Once fused, the pain in the spine disappears, but the patient has a complete loss of spine mobility. These fused spines are particularly brittle and vulnerable to breakage (fracture) when involved in trauma, such as motor vehicle accidents. A sudden onset of pain and mobility in the spinal area of these patients can indicate bone fracture. The lower neck (cervical spine) is the most common area for such fractures.

Chronic spondylitis and ankylosis cause forward curvature of the upper torso (thoracic spine), limiting breathing capacity. Spondylitis can also affect areas where ribs attach to the upper spine, further limiting lung capacity. Ankylosing spondylitis can cause inflammation and scarring of the lungs, causing coughing and shortness of breath, especially with exercise and infections. Therefore, breathing difficulty can be a serious complication of ankylosing spondylitis.

Patients with ankylosing spondylitis can also have arthritis in joints other than the spine. Patients may notice pain, stiffness, heat, swelling, warmth, and/or redness in joints such as the hips, knees, and ankles. Occasionally, the small joints of the toes can become inflamed, or "sausage" shaped. Inflammation can occur in the cartilage around the breast bone (costochondritis) as well as in the tendons where the muscles attach to the bone (tendinitis) and ligament attachments to bone. Some patients with this disease develop Achilles tendinitis, causing pain and stiffness in the back of the heel, especially when pushing off with the foot while walking up stairs.

Other areas of the body affected by ankylosing spondylitis include the eyes, heart, and kidneys. Patients with ankylosing spondylitis can develop inflammation of the iris, called "iritis." Iritis is characterized by redness and pain in the eye, especially when looking at bright lights. Recurrent attacks of iritis can affect either eye. In addition to the iris, the ciliary body and choroid of the eye can become inflamed and this is referred to as uveitis. Iritis and uveitis can be serious complications of ankylosing spondylitis that can damage the eye and impair vision, and may require an eye specialist's (ophthalmologist) urgent care. Special treatments for serious eye inflammation are discussed in the treatment section below. [It should be noted that iritis and inflammation of the spine can occur in other forms of arthritis such as reactive arthritis (formerly Reiter syndrome), psoriatic arthritis, and the arthritis of inflammatory bowel disease.]