Ankylosing spondylitis (AS) is an inflammatory disease that can cause some of the vertebrae in your spine to fuse together. This fusing makes the spine less flexible and can result in a hunched-forward posture. This is characterized by back pain and stiffness that typically appear in adolescence or early adulthood. Over time, back movement gradually becomes limited as the bones of the spine (vertebrae) fuse together. This progressive bony fusion is called ankylosis.If ribs are affected, it may be difficult to breathe deeply.
Ankylosing spondylitis affects men more often than women. Signs and symptoms of ankylosing spondylitis typically begin in early adulthood. Inflammation also can occur in other parts of your body — most commonly, your eyes.
The earliest symptoms of ankylosing spondylitis result from inflammation of the joints between the pelvic bones (the ilia) and the base of the spine (the sacrum). These joints are called sacroiliac joints, and inflammation of these joints is known as sacroiliitis. The inflammation gradually spreads to the joints between the vertebrae, causing a condition called spondylitis. Ankylosing spondylitis can involve other joints as well, including the shoulders, hips, and, less often, the knees. As the disease progresses, it can affect the joints between the spine and ribs, restricting movement of the chest and making it difficult to breathe deeply. People with advanced disease are also more prone to fractures of the vertebrae.
Ankylosing spondylitis affects the eyes in up to 40 percent of cases, leading to episodes of eye inflammation called acute iritis. Acute iritis causes eye pain and increased sensitivity to light (photophobia). Rarely, ankylosing spondylitis can also cause serious complications involving the heart, lungs, and nervous system
There is no cure for ankylosing spondylitis, but treatments can decrease your pain and lessen your symptoms.
Early signs and symptoms of ankylosing spondylitis may include pain and stiffness in your lower back and hips, especially in the morning and after periods of inactivity. Over time, symptoms may worsen, improve or stop completely at irregular intervals.
The areas most commonly affected are:
- The joint between the base of your spine and your pelvis
- The vertebrae in your lower back
- The places where your tendons and ligaments attach to bones, mainly in your spine, but sometimes along the back of your heel
- The cartilage between your breastbone and ribs
- Your hip and shoulder joints
Ankylosing spondylitis has no known specific cause, though genetic factors seem to be involved. It is likely caused by a combination of genetic and environmental factors, most of which have not been identified. However, researchers have found variations in several genes that influence the risk of developing this disorder.
In particular, people who have a gene called HLA-B27 are at significantly increased risk of developing ankylosing spondylitis.
The HLA-B gene provides instructions for making a protein that plays an important role in the immune system. The HLA-B gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex helps the immune system distinguish the body's own proteins from proteins made by foreign invaders (such as viruses and bacteria). The HLA-B gene has many different normal variations, allowing each person's immune system to react to a wide range of foreign proteins. A variation of the HLA-B gene called HLA-B27 increases the risk of developing ankylosing spondylitis. Although many people with ankylosing spondylitis have the HLA-B27 variation, most people with this version of the HLA-B gene never develop the disorder. It is not known how HLA-B27 increases the risk of developing ankylosing spondylitis.
Variations in several additional genes, including ERAP1, IL1A, and IL23R, have also been associated with ankylosing spondylitis. Although these genes play critical roles in the immune system, it is unclear how variations in these genes affect a person's risk of developing ankylosing spondylitis. Changes in genes that have not yet been identified are also believed to affect the chances of developing ankylosing spondylitis and influence the progression of the disorder. Some of these genes likely play a role in the immune system, while others may have different functions. Researchers are working to identify these genes and clarify their role in ankylosing spondylitis.
During the physical exam, your doctor may ask you to bend your back in different directions. He or she may also measure your chest circumference — once with your lungs empty and once with them full of air — to compare the difference.
Your doctor may also try to reproduce your pain by pressing on specific portions of your pelvis or by moving your legs into a particular position. He or she might also ask you to try to stand upright, with your heels and the back of your head against a wall.
X-rays allow your doctor to check for changes in your joints and bones, though the visible signs of ankylosing spondylitis may not be evident early in the disease.
Magnetic resonance imaging (MRI) uses radio waves and a strong magnetic field to provide more-detailed images of bones and soft tissues. MRI scans can reveal evidence of ankylosing spondylitis earlier in the disease process, but are much more expensive.
There are no specific lab tests to identify ankylosing spondylitis. Certain blood tests can check for markers of inflammation, but inflammation can be caused by many different health problems. Your blood can be tested for the HLA-B27 gene, but most people who have that gene don't have ankylosing spondylitis.
Prognosis is related to disease severity. AS can range from mild to progressively debilitating and from medically controlled to refractory. Some cases may have times of active inflammation followed by times of remission resulting in minimal disability, while others never have times of remission and have acute inflammation and pain, leading to significant disability. As the disease progresses, it can cause the vertebrae and the lumbosacral joint to ossify, resulting in the fusion of the spine. This places the spine in a vulnerable state because it becomes one bone, which causes it to lose its range of motion as well as putting it at risk for spinal fractures. This not only limits mobility but reduces the affected person's quality of life. Complete fusion of the spine can lead to a reduced range of motion and increased pain, as well as total joint destruction which could lead to a joint replacement.
Over a long-term period, osteopenia or osteoporosis of the AP spine may occur, causing eventual compression fractures and a back "hump". Typical signs of progressed AS are the visible formation of syndesmophytes on X-rays and abnormal bone outgrowths similar to osteophytes affecting the spine. The fusion of the vertebrae paresthesia is a complication due to the inflammation of the tissue surrounding nerves.
Organs commonly affected by AS, other than the axial spine and other joints, are the heart, lungs, eyes, colon, and kidneys. Other complications are aortic regurgitation, Achilles tendinitis, AV node block and amyloidosis. Owing to lung fibrosis, chest X-rays may show apical fibrosis, while pulmonary function testing may reveal a restrictive lung defect. Very rare complications involve neurologic conditions such as the cauda equina syndrome.
Mortality is increased in people with AS and circulatory disease is the most frequent cause of death;and because increased mortality in ankylosing spondylitis is related to disease severity, factors negatively affecting outcomes include:
Male sexPlus 3 of the following in the first 2 years of disease:Erythrocyte sedimentation rate (ESR) >30 mm/hUnresponsive to NSAIDsLimitation of lumbar spine range of motionSausage-like fingers or toesOligoarthritisOnset <16 years old
The hunched position that often results from complete spinal fusion can have an effect on a person's gait. Increased spinal kyphosis will lead to a forward and downward shift in center of mass (COM). This shift in COM has been shown to be compensated by increased knee flexion and ankle plantarflexion. The gait of someone with ankylosing spondylitis often has a cautious pattern because they have decreased ability to absorb shock, and they cannot see the horizon.
The goal of treatment is to relieve your pain and stiffness, and prevent or delay complications and spinal deformity. Ankylosing spondylitis treatment is most successful before the disease causes irreversible damage to your Joints.
Nonsteroidal anti-inflammatory drugs (NSAIDs) — such as naproxen (Naprosyn) and indomethacin (Indocin) — are the medications doctors most commonly use to treat ankylosing spondylitis. They can relieve your inflammation, pain and stiffness. However, these medications also can cause gastrointestinal bleeding.
If NSAIDs aren't helpful, your doctor may suggest tumor necrosis factor (TNF) blockers. TNF is a cell protein that acts as an inflammatory agent in rheumatoid arthritis. TNF blockers target this protein to help reduce pain, stiffness, and tender or swollen joints. They are administered by injecting the medication under the skin or through an intravenous line.
Examples of TNF blockers include:
- Adalimumab (Humira)
- Etanercept (Enbrel)
- Golimumab (Simponi)
- Infliximab (Remicade)
TNF blockers can reactivate latent tuberculosis and may cause certain neurological problems.
Physical therapy can provide a number of benefits, from pain relief to improved physical strength and flexibility. Your doctor may recommend that you meet with a physical therapist to provide you with specific exercises designed for your needs.
Range-of-motion and stretching exercises can help maintain flexibility in your joints and preserve good posture. Proper sleep and walking positions and abdominal and back exercises can help maintain your upright posture.
Most people with ankylosing spondylitis don't need surgery. However, your doctor may recommend surgery if you have severe pain or joint damage, or if your hip joint is so damaged that it needs to be replaced.