History and exam
Key diagnostic factors
common
presence of risk factors
inflammatory back pain
iritis/uveitis
enthesitis
presentation in late teens and early 20s
People can present at any age, but symptoms usually develop in late adolescence and the early 20s.[94]
male sex
positive family history of ankylosing spondylitis (AS)
Other diagnostic factors
common
fatigue
Fatigue is extremely common in ankylosing spondylitis; the level of fatigue can be used as a surrogate marker for disease activity.[96]
sleep disturbance
Sleep disturbance is common in patients with ankylosing spondylitis (AS). Sleep quality (estimated sleep time, sufficiency index, and number of awakenings per night) is poorer in patients with AS, compared with controls.[97]
tenderness at sacroiliac joint
Due to inflammatory process of disease.
dyspnoea
Can be present if there is costochondral joint involvement causing limitation in chest expansion.
Also may be due to spinal kyphosis resulting in limitation of lung expansion.
loss of lumbar lordosis
Classic examination finding.
peripheral joint involvement
Peripheral joints may be affected: for example, hip joints, costovertebral joints.
Women tend to have more cervical and peripheral joint pain than men, and are more likely to have peripheral arthritis.[17]
kyphosis
Common in advanced disease.
uncommon
psoriasis
Psoriasis can be present in patients with ankylosing spondylitis (AS) at a frequency of approximately 10%.[84][98][99]
It is very important that patients with AS found to have concomitant psoriasis are not classified as having psoriatic spondylitis or psoriatic arthritis.
The presence of syndesmophytes (osseous excrescence attached to a ligament) in the spine is characteristic of AS.
Risk factors
strong
HLA-B27
HLA-B27 is present in about 90% of patients who have ankylosing spondylitis (AS).[18] The prevalence of HLA-B27 varies among ethnic communities in the US, with 7.5% of non-Hispanic white, 4.6% of Mexican-American, and 1.1% of non-Hispanic black people being HLA-B27 positive.[19] HLA-B27 contribution to the total genetic risk for AS is, however, relatively modest (approximately 20%).[20][21]
endoplasmic reticulum aminopeptidase 1 (ERAP1) and interleukin-23 receptor (IL23R) gene polymorphisms
IL23R and ERAP1 (also known as aminopeptidase regulator of tumour necrosis factor receptor 1 shedding [ARTS1]) polymorphisms have been identified as being responsible for approximately 9% and 26% of the risk for developing AS, respectively.[43]
ERAP1 is believed to be responsible for the preparation of peptides for the major histocompatibility class 1 presentation, and IL23R is thought to be pivotal in the regulation of Th17 cells, which express high levels of pro-inflammatory cytokines.[44]
positive family history of ankylosing spondylitis (AS)
There is a 16-fold increased risk of developing AS among HLA-B27-positive first-degree relatives of HLA-B27-positive probands with AS, compared with HLA-B27-positive individuals in the population at large.[79]
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