Bechterew's syndrome (ankylosing spondylitis). A syndrome with distinct subgroups

The results of tests for associations among radiographic findings of the dorsolumbar spine, peripheral joints, tendon insertions and the pubic symphysis are presented. Ankylosis of sacro-iliac joints, ankylosis of apophyseal joints, bridging syndesmophytes, ossified interspinous ligament, block vertebrae, arthritis of the pubic symphysis and new bone formation of the ischium were strongly mutually associated. They probably belong to the same subgroup of disease. Such findings were negatively associated with distal peripheral joint arthritis. Mixed osteophytes, parasyndesmophytes or shining corners (anterior spondylitis) showed associations suggesting that the etiology may be mixed. A late stage of sacro-iliitis, regressive changes, characterized by narrow joint spaces without extensive ankylosis and with minimal sclerosis (grade IV sacro-iliitis) was associated with distal peripheral joints arthritis, but negatively associated with signs of ankylosing processes of the dorsolumbar spine. On the basis of the radiographic findings, distinct subgroups of AS could be identified. These results confirm our previous results of an association pattern between clinical findings. We would also recommend that the grading system of sacro-iliitis put forward by Dale be adopted, since it turned out that this grading system often distinguished between distinct subgroups of this heterogeneous condition(s).