Spondyloarthritis and ankylosing spondylitis

Spondyloarthritis, formerly called spondyloarthropathies and now also known as axial arthritis, is not a single disease. It is a group of conditions that share certain clinical features.

This group includes:

Ankylosing spondylitis.
Psoriatic arthritis.
Arthritis associated with inflammatory bowel diseases such as Crohn's disease.
Reactive arthritis.

Although they belong to the same family, they do not all present in the same way or occur with the same frequency.

Ankylosing spondylitis

Ankylosing spondylitis primarily affects the axial skeleton, particularly the spine and sacroiliac joints.

It should be suspected when a young person has low-back pain with inflammatory features. It generally begins before age 50.

Inflammatory back pain behaves differently from mechanical pain:

It worsens with rest.
It may wake the patient at night.
It is accompanied by stiffness.
It improves after the person gets up and begins moving.

A young person with persistent low-back pain should not automatically be diagnosed with muscle spasm, wear and tear or sciatica. The first question is whether the pain pattern suggests inflammation.

The disease begins in the sacroiliac joints

Inflammation may begin in the sacroiliac joints, located where the spine meets the pelvis.

At early stages, changes may be subtle and not yet visible on conventional X-rays. The absence of radiographic abnormalities does not exclude the disease.

Waiting for an X-ray to show clear changes may mean waiting many years.

X-ray changes may take five to ten years

The characteristic changes of ankylosing spondylitis may take approximately five to ten years to appear on an X-ray.

Therefore, when an X-ray finally demonstrates the disease, it may already be showing a late stage.

At advanced stages, the so-called bamboo spine can appear. By then, substantial and irreversible structural damage is already present.

The goal should be to diagnose the disease before that stage, not to wait for obvious damage before accepting that it exists.

Sacroiliac MRI and the ASAS protocol

Spondyloarthritis is a group of diseases, not a single condition. It includes ankylosing spondylitis, arthritis associated with psoriasis, inflammatory bowel disease-related arthritis and reactive arthritis, among others.

An important characteristic of this group is its ability to cause inflammation in the axial skeleton, mainly the spine and sacroiliac joints. It may also affect peripheral joints such as a knee, ankle or even a finger.

A historical problem in early diagnosis is that characteristic X-ray changes may take many years to appear. When clinical suspicion exists, magnetic resonance imaging can look for inflammation before an X-ray shows evident structural lesions.

Specific MRI sequences are used to study the sacroiliac joints, commonly known as the ASAS protocol. In most cases today, inflammatory changes can be identified without administering contrast material.

The different sequences assess both inflammatory activity and structural damage. Fluid-sensitive sequences such as STIR can detect bone-marrow edema related to active inflammation, while other sequences identify structural changes caused by the disease.

MRI is not interpreted in isolation. It is integrated with symptoms, physical examination, history and the patient's other studies. It may provide highly valuable information about whether axial spondyloarthritis is present and whether there are signs of active inflammation or structural lesions.

This is why a rheumatologist may request an MRI of the sacroiliac joints using a specific spondyloarthritis protocol.

HLA-B27 does not make the diagnosis

In Latin America, I do not consider HLA-B27 useful for diagnosing ankylosing spondylitis.

I have treated patients with advanced disease, including a clearly visible bamboo spine on X-rays, whose HLA-B27 result was negative.

I discussed this directly with Mohammed Asim Khan, a world authority on ankylosing spondylitis. When I explained that I found patients with evident disease and negative HLA-B27, his response was that we probably did not know how to perform the test correctly.

I replied that I sent the samples to Quest in the United States, where the same procedure was used, and the results remained negative. I even offered to show him those patients' X-rays.

My conclusion is direct: in Latin America, no time should be wasted waiting for this test. It does not make the diagnosis of spondylitis.

Diagnosis should rest on the medical history, examination and appropriate imaging—not on waiting for a genetic marker to authorize the physician to recognize a disease the patient already has.

Psoriatic arthritis

Psoriatic arthritis belongs to the same group.

Psoriasis may appear before the arthritis, but it can also develop later. Therefore, the initial absence of obvious skin lesions does not completely exclude this possibility.

The arthritis may have an asymmetric distribution. Examination of the skin and nails provides important information and should not be omitted.

The physician should actively look for these manifestations because some changes may be subtle and the patient may not connect them with joint pain or swelling.

Arthritis associated with Crohn’s disease

Inflammatory bowel diseases, including Crohn's disease, can also be associated with arthritis.

In my practice this presentation is uncommon, but it belongs to the group and should be considered when the history suggests inflammatory bowel disease.

This does not mean ordering gastrointestinal studies indiscriminately for everyone with low-back pain. There must first be a clinical reason to investigate the relationship.

Reactive arthritis

Reactive arthritis also belongs to this group, although it is rare in my experience.

It may present as monoarthritis or oligoarthritis—inflammation of one or a few joints. Eye inflammation may also occur.

The combination of asymmetric arthritis and an inflamed eye should be considered carefully within the patient's complete history.

Diagnose before damage becomes irreversible

Ankylosing spondylitis may progress for years before showing classic radiographic abnormalities.

Waiting for a clearly positive X-ray or relying on HLA-B27 may delay diagnosis unnecessarily. Once advanced deformities appear, they are irreversible.

The key is to recognize inflammatory pain, examine the patient and promptly request the correct study of the sacroiliac joints.

The objective is not simply to attach a label. It is to identify the disease while there is still time to control inflammation and prevent continued permanent damage.