Ankylosing Spondylitis: What Kind of Disease It Is and How It Is Recognized

The diagnosis of "ankylosing spondylitis" often comes as a surprise: for years a person has attributed morning stiffness and aching lower back pain to fatigue or sciatica. Below — what this disease is, how it differs from other forms of spondylitis, and how it is recognized.

What ankylosing spondylitis is and why it is called Bechterew's disease

Ankylosing spondylitis is a chronic disease in which the spine and other areas of the body become inflamed; it is a form of axial spondyloarthritis. Inflammation occurs between the vertebrae and in the joints between the spine and the pelvis, stiffness appears, and over time the vertebrae may fuse — a stooped posture develops.

Its second name is Bechterew's disease (in full form — Strümpell–Bechterew–Marie disease); it is sometimes called rheumatoid spondylitis, although it is a separate disease distinct from rheumatoid arthritis.

Spondylitis, spondyloarthritis, axial and peripheral: what the difference is

Spondylitis is inflammation in the spine; spondyloarthritis is the general name for a group of inflammatory joint diseases. Since 2009, ankylosing spondylitis has been included in the group of axial spondyloarthritides: the radiographic variant is ankylosing spondylitis itself with changes visible on imaging, while the non-radiographic variant comprises early forms, when X-rays are clear but MRI shows changes.

Axial means along the axis: the spine and the sacroiliac joints. Peripheral spondyloarthritis affects large joints: elbows, knees, ankles. Bechterew's disease differs from rheumatoid arthritis in that it has no rheumatoid nodules and no rheumatoid factor in the blood.

Causes and who is affected more often, including women

The cause is unknown; an association with a variant of the HLA-B27 gene is observed, and a family predisposition is significant. The frequency of the disease follows the frequency of this antigen: from 0.15% of the adult population in France to 1.4% in Norway. Onset is usually at age 20–30, with onset before age 45. According to some data, men are affected more often and more severely; according to others, women and men are affected equally.

Main symptoms and how the disease develops

The most common sign is pain and stiffness in the lower back and pelvic area. The pain is worse at night and after prolonged sitting, and decreases with movement; stiffness increases in the second half of the night and toward morning. Symptoms develop gradually, over months and years. Pain and swelling of other joints, inflammation at the site where a tendon attaches to bone, and pronounced fatigue are added. The disease must be distinguished from osteochondrosis and spondylosis.

Subsequently the pain spreads throughout the spine, stooping and curvature appear, and the chest expands less well. Extraskeletal manifestations include iritis and iridocyclitis, visual changes, skin rashes, abdominal pain, and loose stools.

How ankylosing spondylitis is diagnosed

There is no single test that confirms the diagnosis. The doctor asks about complaints and family history, performs an examination, and orders blood tests and imaging. X-rays will show changes, but at the first stage the image may be clear — then MRI helps. ESR is often elevated. The disease is distinguished from osteochondrosis and spondylosis: in Bechterew's disease, pain intensifies at rest and during sleep.

• the nature of pain and stiffness: at night, at rest, after prolonged sitting;
• age at onset and duration of complaints;
• family history, psoriasis, bowel diseases;
• range of motion in the spine and chest;
• blood tests, imaging, or MRI.

Complications and when to see a rheumatologist

The prognosis varies: in some people the condition improves after the initial period of inflammation, while in others it progresses slowly. With fusion of the vertebrae and involvement of the hip or knee joints, severe disability is possible. Complications include osteoporosis and spinal fractures, and cardiovascular diseases; with current treatment approaches, life expectancy is usually not substantially affected.

The disease itself is not a reason to call an ambulance; 103 or 112 — for life-threatening signs, such as symptoms of a stroke or heart attack.

Referral to a rheumatologist is made for persistent back symptoms. Before the visit, write down: when and at what age the complaints began, whether the pain intensifies at rest and at night, whether relatives have Bechterew's disease, psoriasis, or bowel diseases, and what previous tests and imaging showed. This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer