Epidemiology of Sacroiliitis and Axial Spondyloarthritis in Children

Risk Based on HLA‑B27 Status

• In individuals who are HLA‑B27 negative, the lifetime risk of developing axial spondyloarthritis (axSpA) is approximately 3 %. 1
• In HLA‑B27 positive first‑degree relatives of affected patients, the lifetime risk of axSpA rises to roughly 25 %. 1

Overall Prevalence and Typical Age of Onset

• The global prevalence of ankylosing spondylitis (AS) – the prototypical form of axSpA – ranges from 0.14 % to 0.25 % in the general population, with disease onset most commonly occurring in late adolescence or early adulthood. 2

Probability of Disease at Age 10

• Even among high‑risk groups (e.g., HLA‑B27 positive relatives), the probability of having sacroiliitis or axSpA at 10 years of age remains very low, because clinical manifestation typically appears in the second to third decade of life. 2