Ankylosing Spondylitis

Ankylosing spondylitis is inflammation of the spine and large joints, resulting in stiffness and pain.

The disease is 3 times more common in men than in women, developing most commonly between the ages of 20 and 40. Its cause is not known, but the disease tends to run in families, indicating that genetics plays a role. Ankylosing spondylitis is 10 to 20 times more common in people whose parents or siblings have it.

Symptoms

Mild to moderate flare-ups of inflammation generally alternate with periods of almost no symptoms.

The most common symptom is back pain, which varies in intensity from one episode to another and from one person to another. Pain is often worse at night and in the morning. Early morning stiffness that is relieved by activity is also very common. Pain in the lower back and the associated muscle spasms are often relieved by bending forward. Therefore, people often assume a stooped posture, which can lead to a permanent bent-over position. In others, the spine becomes noticeably straight and stiff.

Loss of appetite, weight loss, fatigue, and anemia can accompany the back pain. If the joints connecting the ribs to the spine are inflamed, the pain may limit the ability to expand the chest to take a deep breath. Occasionally, pain starts in large joints, such as the hips, knees, and shoulders.

One third of the people have recurring attacks of mild eye inflammation, which usually does not impair vision. In a few people, inflammation of a heart valve results in a permanently damaged valve. If the damaged vertebrae press against nerves or the spinal cord, numbness, weakness, or pain can develop in the area supplied by the affected nerves. The cauda equina (horse's tail) syndrome is a rare complication (see Section 6, Chapter 93).

Diagnosis

The diagnosis is based on the pattern of symptoms and on x-rays of the spine and affected joints, which show a wearing away (erosion) of the joint between the spine and the hip bone (sacroiliac joint) and the formation of bony bridges between the vertebrae, making the spine stiff. The erythrocyte sedimentation rate (ESR), a test that measures the rate at which red blood cells settle to the bottom of a test tube containing blood, tends to be high, indicating inflammation. In addition, a specific gene, HLA-B27, is found in about 90% of people who have this disease; however, because this gene is also found in about 6 to 7% of healthy white people, its presence is of limited value in diagnosis.

Prognosis and Treatment

Most people develop some disabilities but can still lead normal, productive lives. In some people, the disease is more progressive, causing severe deformities.

Treatment focuses on relieving back and joint pain and preventing or correcting spinal deformities. Nonsteroidal anti-inflammatory drugs (NSAIDs) (see Section 5, Chapter 67 and Section 6, Chapter 78) can reduce the pain and inflammation, thus enabling people to do important exercises to retain posture, including stretching and deep breathing. Sulfasalazine may help the pain in joints other than those of the back. The tumor necrosis factor (TNF) inhibitors etanercept or infliximab can relieve the pain and inflammation.

Corticosteroids help only in the short-term treatment of inflammation of the eyes and of joints other than the spine. Muscle relaxants and opioid analgesics are usually used for only brief periods to relieve severe pain and muscle spasms. If hips or knees become eroded or fixed in a bent position, surgery to replace the joint can relieve pain and restore function.

The long-range goals of treatment are to maintain proper posture and develop strong back muscles. Daily exercises strengthen the muscles that oppose the tendency to bend and stoop. It has been suggested that people spend some time each day--often while reading--lying on their stomach propped up on their elbows; this position extends the back and helps to prevent too much flexion.