ANKYLOSING SPONDYLITIS

INTRODUCTION –

The word is from Greek ankylos meaning stiffening, spondylos meaning vertebra, and -itis meaning inflammation.

Ankylosing spondylitis (AS) is a type of arthritis in which there is long term inflammation of the joints of the spine. Typically the joints where the spine joins the pelvis are also affected. Occasionally other joints such as the shoulders or hips are involved. Eye and bowel problems may also occur. Back pain is a characteristic symptom of AS, and it often comes and goes. Stiffness of the affected joints generally worsens over time.

Although the cause of ankylosing spondylitis is unknown, it is believed to involve a combination of genetic and environmental factors. More than 90% of those affected have a specific human leukocyte antigen known as the HLA-B27 antigen. The underlying mechanism is believed to be autoimmune or autoinflammatory. Diagnosis is typically based on the symptoms with support from medical imaging and blood tests. AS is a type of seronegative spondyloarthropathy, meaning that tests show no presence of rheumatoid factor (RF) antibodies. It is also within a broader category known as axial spondyloarthritis.

There is no cure for ankylosing spondylitis. Treatments may improve symptoms and prevent worsening. This may include medication, exercise, and surgery. Medications used include NSAIDs, steroids, DMARDs such as sulfasalazine, and biologic agents such as infliximab.

Between 0.1% and 1.8% of people are affected. Onset is typically in young adults. Males are more often affected than females. The condition was first fully described in the late 1600s by Bernard Connor, but skeletons with ankylosing spondylitis are found in Egyptian mummies.

Signs and symptoms-

The signs and symptoms of ankylosing spondylitis often appear gradually, with peak onset being between 20 and 30 years of age. Initial symptoms are usually a chronic dull pain in the lower back or gluteal region combined with stiffness of the lower back. Individuals often experience pain and stiffness that awakens them in the early morning hours.

Pathophysiology

The ankylosis process

Ankylosing spondylitis (AS) is a systemic rheumatic disease, meaning it affects the entire body. Approximately 90% of people with AS express the HLA-B27 genotype, meaning there is a strong genetic association. 1–2% of individuals with the HLA-B27 genotype develop the disease. Tumor necrosis factor-alpha (TNF α) and IL-1 are also implicated in ankylosing spondylitis. Autoantibodies specific for AS have not been identified. Anti-neutrophil cytoplasmic antibodies (ANCAs) are associated with AS, but do not correlate with disease severity.

The association of AS with HLA-B27 suggests the condition involves CD8 T cells, which interact with HLA-B. This interaction is not proven to involve a self-antigen, and at least in the related reactive arthritis, which follows infections, the antigens involved are likely to be derived from intracellular microorganisms.[citation needed] There is, however, a possibility that CD4+ T lymphocytes are involved in an aberrant way, since HLA-B27 appears to have a number of unusual properties, including possibly an ability to interact with T cell receptors in association with CD4 (usually CD8+ cytotoxic T cell with HLAB antigen as it is a MHC class 1 antigen).

"Bamboo spine" develops when the outer fibers of the fibrous ring (annulus fibrosus disci intervertebralis) of the intervertebral discs ossify, which results in the formation of marginal syndesmophytes between adjoining vertebrae.

Diagnosis

 (1) radiographic axial spondyloarthritis (which is a synonym for ankylosing spondylitis) and

(2) non-radiographic axial spondyloarthritis (which include less severe forms and early stages of ankylosing spondylitis)

Radiographic features

The earliest changes in the sacroiliac joints demonstrable by plain x–ray shows erosions and sclerosis.

Progression of the erosions leads to pseudo-widening of the joint space and bony ankylosis.

X-ray spine can reveal squaring of vertebrae with spine ossification with fibrous band run longitudinally called syndesmophyte while producing bamboo spine appearance.

A drawback of X-ray diagnosis is the signs and symptoms of AS have usually been established as long as 8–10 years prior to X-ray-evident changes occurring on a plain film X-ray, which means a delay of as long as 10 years before adequate therapies can be introduced. Options for earlier diagnosis are tomography and MRI of the sacroiliac joints, but the reliability of these tests is still unclear.

T1-weighted MRI with fat suppression after administration of gadolinium contrast showing sacroiliitis in a patient with ankylosing spondylitis

Genetic testing

Variations of the HLA-B gene increase the risk of developing ankylosing spondylitis, although it is not a diagnostic test. Those with the HLA-B27 variant are at a higher risk than the general population of developing the disorder. HLA-B27, demonstrated in a blood test, can occasionally help with diagnosis, but in itself is not diagnostic of AS in a person with back pain. Over 90% of people that have been diagnosed with AS are HLA-B27 positive, although this ratio varies from population to population (about 50% of African Americans with AS possess HLA-B27 in contrast to the figure of 80% among those with AS who are of Mediterranean descent.

Surgery

In severe cases of AS, surgery can be an option in the form of joint replacements, particularly in the knees and hips. Surgical correction is also possible for those with severe flexion deformities (severe downward curvature) of the spine, particularly in the neck, although this procedure is considered very risky.

Physical therapy

Though physical therapy remedies have been scarcely documented, some therapeutic exercises are used to help manage lower back, neck, knee, and shoulder pain. Some therapeutic exercises include:

Low intensity aerobic exercise

Transcutaneous electrical nerve stimulation (TENS)

Thermotherapy

Proprioceptive neuromuscular facilitation (PNF)

Exercise programs, either at home or supervised

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.