Reactive arthritis.

Although sometimes used to refer to any sterile arthritis occurring in association with infection, the term 'reactive arthritis' is better reserved for arthritis following sexually acquired nonspecific urethritis or enteric infections with organisms such as Shigella, Salmonella, Yersinia and Campylobacter, because these arthropathies are unified by a number of shared clinical characteristics and an association with HLA B27. This review suggests that these arthropathies may also share a common pathogenic pathway, triggered by an ' arthritogenic factor' common to the diverse microbes which cause the disease and modified by genetic factors other than HLA B27. Although uncommon, reactive arthritis is important because it could provide the key to understanding the other seronegative arthropathies and mechanisms basic to chronic inflammatory synovitis.