[Extraspinal erosions of tendon insertions in ankylosing spondylitis].

A study based on the clinical observation of 9 adults carrying the HLA B27 antigen. Seven of these patients had a typical ankylosing spondylitis with bilateral sacro-iliitis. The other two cases were considered to have a minor form of the disease, without sacro-iliitis. In various zones of tendinous or ligamentous insertion (on the calcaneal and ischial tuberosities, the anterior tibial tuberosity, the patella, the lateral femoral condyle, the metataŕso-phalangeal epiphyses of the index finger, the head of the humerus), the patients complained of pain and presented radiological images of more or less developed bony erosion. These erosion of insertions are not specific to ankylosing spondylitis, but they can be suggestive of the diagnosis. They can be an important element in the diagnosis of pre-spondylitic forms, especially in adolescents. Certain histological findings suggest that these lesions are a form of localized algodystrophy.