How does the prevalence of ankylosing spondylitis (AS) and undifferentiated spondyloarthropathy (USpA) vary by age?

Updated: Feb 02, 2021
  • Author: Lawrence H Brent, MD; Chief Editor: Herbert S Diamond, MD  more...
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The age of onset of AS is usually from the late teens to age 40 years. Approximately 10%-20% of all patients experience symptom onset before age 16 years; in such patients, the disease is referred to as juvenile-onset AS. Onset of AS in persons older than 50 years is unusual, although a diagnosis of mild or asymptomatic disease may be made at a later age. [56]   Uncommonly, patients may not come to medical attention until they have advanced disease.

There is often a significant delay in diagnosis, usually occurring several years after the onset of inflammatory rheumatic symptoms. In a study of German and Austrian patients with AS, the age of onset of disease symptoms was 25 years in HLA-B27–positive and 28 years in HLA-B27–negative patients, with a delay in diagnosis of 8.5 years in HLA-B27–positive and 11.4 years in HLA-B27–negative patients. [57]

In a study of Turkish patients with AS, the age of onset of disease symptoms was 23 years, with a delay in diagnosis of 5.3 years in HLA-B27–positive patients and 9.2 years in HLA-B27–negative patients. [58] Patients with inflammatory back pain or a positive family history of AS had a shorter diagnostic delay.

USpA is generally found in young to middle-aged adults but can develop from late childhood into the fifth decade of life. [59]

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