ABSTRACT

Although nowadays ankylosing spondylitis (AS), also known as Morbus Bechterew or Bechterew’s disease, is a well-recognized entity, it should be noted that this disease for a long time (up to the early 1960s) had been regarded as a variant of rheumatoid arthritis (RA) (1,2). The disease was often referred to as rheumatoid spondylitis. At that time Wright and Moll had proposed the unifying concept of the spondyloarthropathies or spondylarthritides (SpA) (3). With the advent of classification criteria and improved epidemiological tools, and also due to thorough clinical research, and the important contribution of human leukocyte antigen (HLA)-typing it became quite clear that AS is in fact the prototype of this group of related diseases (4). The modified New York criteria, in which the presence of radiographic sacroiliitis was made a conditio sine qua non for the diagnosis of AS have had widespread acceptance for standardization of surveys of the disease among populations (5). In daily practice, however, occasionally clinical cases of AS without radiographic sacroiliitis may occur (6). It is now known that magnetic resonance imaging (MRI) techniques are more sensitive in detecting inflammation of the sacroiliac joints among symptomatic people than conventional radiographs or computer tomographic imaging of these joints (7–9). The idea, therefore, is that conventional radiography may lack sensitivity to detect these occasional patients who otherwise may show all usual signs and symptoms of AS. It should also be noted that dealing with sacroiliitis there is considerable intra- and inter-observer variation in the interpretation of conventional radiographs of the sacroiliac joints (10).