Inflammatory rheumatic condition mainly affecting the spine that causes progressive stiffness and pain

It is part of the seronegative spondyloarthropathy group of conditions relating to the HLA B27 gene. Other conditions in this group are reactive arthritis and psoriatic arthritis.

Main joints affected - vertebral column and SIJ - Can progress to fusion of these joints = bamboo spine appearance on x-ray

Risk factors:

• HLA-B27 (90% of patients with AS have this gene, 2% of those with the gene get AS. This number is 20% if a first degree relative is affected)
• Family history
• <40yrs age

PC

Gradual development of Sx - more then 3 months

Main feature - lower back pain and stiffness & SI pain in the buttock region

• worse with rest, improves with movement
• Pain worse at night (may awake from sleep) & morning
• Takes 30mins for stiffness to improve, gets better through the day

Examination:

• Schober’s test - less then 20cm (or distance does not increase by 5cm) =restricted movement, supports diagnosis of AS
• Wall to tragus test
• Chest expansion test - restrictive lung disease