Ankylosing Spondylitis Ankylosing Spondylitis Ankylosing spondylitis occurs in both sexes but is usually milder, and therefore less frequently diagnosed, in women.
Recent estimates suggest that it is three times more common in men.
The prevalence in different ethnic groups is related to the frequency of HLA-B27 in these populations. Bony ankylosis is most frequent and the sacro-iliac joints often become fused. The disease is characterised by bilateral sacro-iliitis. As the disease extends up to the intervertebral joints, there is 'squaring' of the vertebral bodies radiologically, seen on the lateral view and calcification of the annulus fibrosus giving the characteristic syndesmophytes which fuse to form the classic 'bamboo spine'. The disease most commonly begins between 16 and 40 years of age.