[Clinical and serological characterization of Chlamydia-induced arthritis].

Chlamydia-induced arthritis was diagnosed in 32 patients (18 men and 14 women; mean age 33 [17-54] years). 13 were HLA-B27 positive. In 19 patients the arthritis was largely confined to one joint. Enthesopathies occurred in 14 patients, and in 13 sacroiliitis was diagnosed radiologically. The most frequent extra-articular changes affected the urogenital system (26 cases). The full Reiter syndrome was present in seven patients (four men, three women). All patients had serum antibodies against Chlamydia. In 16 patients Chlamydia was diagnosed as the causative organism by urogenital swab. Chlamydia-induced arthritis differs from other arthritides in the high proportion of HLA-B27 negative patients.