Undifferentiated arthritis in an early synovitis out-patient clinic

To describe the features of undifferentiated arthritis in an early synovitis out-patient clinic.

In a two-year prospective cohort study 320 patients with rheumatic symptoms of less than one year were investigated in an early synovitis out-patient clinic. Besides the clinical parameters, an intensive laboratory program was performed, including routine blood and serum parameters, immunological investigations (CRP, IgG,A,M,C3C4,RF,ANA, DNA, HLA B-27), and a microbiological program to search for reactive arthritis-inducing infections.

217 patients had inflammatory rheumatic diseases, of whom only 100 (46%) could be given a definite diagnosis, whereas 117 (54%) were considered as having undifferentiated arthritis (UA). Patients with UA had a mean age of 41 +/- 15 years, the sex-ratio was 1.8:1.0 (f/m), joint manifestations were oligoarticular in 68%, monarticular in 14%, and polyarticular in 18%. Rheumatoid factor was positive in 17%, HLA-B27 was found in 27%, and 21% of the patients had a history of recent infection. Follow up over 26 (range 4-38) months of 28 (24%) patients with UA revealed complete remission in 15 patients (54%), while 10 patients (36%) had further UA with partial remission, unchanged activity or progressive disease, and only 2 (7%) developed rheumatoid arthritis (RA) and 1 (4%) was diagnosed as having ankylosing spondylitis.

Most patients with early synovitis followed at our clinic remain unclassified with a good prognosis.