Ankylosing Spondylitis (AS) is a form of arthritis that affects the joints in the spine. It mainly occurs in the sacroiliac joint where the spine joins the pelvis. The inflammation in the sacroiliac joint and spine can cause pain and stiffness. Some people have other joints, such as the shoulders, ribs, hips, knees and feet, that are affected. It can also affect tendons, ligaments and organs such as the eyes, bowel, heart and lungs.
Ankylosing Spondylitis often presents during the teen and young adult years. A majority of people with AS develop symptoms before age 30. Only five percent of people develop symptoms after age 45. It affects about twice as many men as women.
The cause of AS is unknown, but scientists believe it is a combination of genes passed from parents to children, along with factors in the environment. The main gene for people at risk for AS is called HLA–B27. However, only one out of 20 people that have this gene develop AS. Two additional genes (IL23R and ERAP1) were recently discovered that also carry a genetic risk for a person to develop AS. Factors in the environment that can trigger the disease in people who have a genetic risk are infections or normal bacteria that live in the intestines.
Most people with AS have mild back pain that comes and goes. Over time, people may have constant pain and can lose flexibility in the spine. In severe cases, the swelling in the spine can cause two or more bones of the spine to fuse. This can cause the rib cage to stiffen and affect how the lungs work.
A doctor will diagnose AS based largely on medical history and a physical exam. Other tests such as x-rays or blood tests may be used to help in confirming the diagnosis.
- Medical history
- The doctor will ask the patient about their pain, whether they have any other medical conditions and if any family members have back problems or arthritis.
- Physical exam
- The doctor will check if the patient has any pain along the spine and/or pelvis, sacroiliac joints, heels or chest. The patient may also be asked to move and bend in different directions to check the flexibility of the spine.
- Changes in the spine and sacroiliac joints may be seen on an x-ray. However, these changes can be seen only after years of inflammation that causes the damage.
- Magnetic resonance imaging (MRI)
- This test can show damage to soft tissue and bone before it can be seen on an x-ray.
- Blood test
- The main blood test used checks for the HLA-B27 gene. This gene is not always present in people with AS. Less than 8 percent of Americans that have the gene actually develop AS. If the gene is present in someone that has symptoms of AS, it may help support the diagnosis of AS.
There is no cure for AS. The goals of treatment are to relieve symptoms and to prevent the disease from progressing. Most people are treated with a combination of medications and exercise. Surgery may also be used to repair some of the joint damage that may occur.
Doctors use a variety of approaches to treat AS that are often used in combinations. The most commonly used treatments are:
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- These medications are commonly used to relieve pain and inflammation. Some people seem to respond better to one NSAID than another. Examples of NSAIDs are aspirin, ibuprofen and naproxen.
- Disease-modifying anti-rheumatic drugs (DMARDs)
- These medications help control the disease process and help reduce inflammation. The most commonly used DMARD for AS is sulfasalazine.
- Injections of corticosteroids directly into the affected joint can offer quick but only temporary pain relief. Injections may be given in the sacroiliac joint, hip joint or knee. They cannot be given in the spine.
- Biologic agents
- This class of medications help relieve symptoms when NSAIDs or other treatments have not worked. They are given by infusion or injection.
Sometimes side effects can disrupt a person’s life and day-to-day activities. However, it is important that a person never change their dosage or stop taking their medication without talking to their doctor or pharmacist.
Common side effects for the different treatment options for AS include:
- Nausea, vomiting, heartburn, diarrhea and headache
- Nausea, vomiting, diarrhea, weakness, liver damage and increased risk of developing an infection
- Weight gain, increased appetite, anxiety, nervousness and increased risk of developing an infection. Steroids may also interfere with normal growth in children.
- Biologic agents
- Cough, nausea, vomiting, rash, weakness, abdominal pain and increased risk of infection
There are many resources and organizations available to help, providing support, advocacy and information:
National Institutes of Health. NIAMS. Handout on Questions and Answers about Ankylosing Spondylitis. NIH Publication No. 10-7609. November 2010.
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