Which HLA-B27 associated axial inflammatory arthritis presents with inflammatory back pain and improves with exercise?

• A. Rheumatoid arthritis
• B. Gout
• C. Ankylosing spondylitis
• D. Psoriatic arthritis

Answer: (C)

Inflammatory back pain that gets better with exercise is a hallmark of axial spondyloarthritis, most classically represented by ankylosing spondylitis, and this condition is strongly associated with HLA-B27. Inflammatory back pain typically starts before age 40, is worse at night with relief by activity, and is associated with morning stiffness. The presence of HLA-B27 increases the likelihood of this diagnosis when such back pain is present.

Rheumatoid arthritis usually presents with a peripheral, symmetric joint pattern and is not defined by back pain that improves with exercise; it’s more linked with RF and anti-CCP positivity. Gout presents as acute, monoarticular flares due to urate crystals, not a chronic axial back pain pattern. Psoriatic arthritis can involve the spine and may be HLA-B27 positive, but the classic presentation of inflammatory back pain that improves with exercise points most strongly to ankylosing spondylitis.