[Concept and criteria of spondylarthritis].

Since several rheumatic disease share common features, they led to the concept of the spondarthritides: ankylosing spondylitis, psoriatic arthritis, reactive arthritis, enteropathic arthritides, juvenile oligoarthritis (type II), and questionable pustolotic arthro-osteitis and Behçet's disease. Furthermore undifferentiated spondarthritides have to be considered. They occur more frequently than ankylosing spondylitis. Definite ankylosing spondylitis is classified according to the New York-criteria, which, however, do not identify the early stage of the disease. In these cases early diagnostic criteria proved to be useful. In a multicenter study the so-called ESSG-criteria were recently introduced for the classification of the whole group of spondarthritides. They are also helpful for the nosological classification of undifferentiated spondarthritides.