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.
