Clinical features and disease outcomes of undifferentiated arthritis in Thailand

Abstract

Background: Undifferentiated arthritis (UA) comprises arthritis not yet identifiable as a specific rheumatic disease. Few reports exist on the natural course of UA in Thai patients.

Objective: To study the clinical features and natural course of UA in Thai patients.

Method: A retrospective, analytical study was performed among Thai patients diagnosed with UA seen at Srinagarind Hospital, Khon Kaen, Thailand, between January 2002 and December 2007.

Results: The medical records of 95 UA patients were reviewed. The mean age at onset was 40.7 ± 14.7 years (range, 15-78). The female:male ratio was 1.25 : 1.00. Common presentations included asymmetrical oligoarthritis followed by polyarthritis. The knee was the most commonly affected joint, followed by the wrist and ankle. Complete remission occurred within 6 months of onset in 4.2% of cases. A diagnosis was specified in 29 patients (30.5%) during the follow-up period (which averaged 17.1 ± 24.0 months [range, 6-84]), including reactive arthritis (in 9 patients), undifferentiated spondyloarthropathy (7), rheumatoid arthritis (6), psoriatic arthritis (4), ankylosing spondylitis (1), gout (1) and unclassified connective tissue disease (1). UA was the default diagnosis for 66 patients (69.5%) after 24 months of follow-up. Hyperglobulinemia was correlated with persistent arthritis (i.e., > 6 months, P = 0.045). The only predictive factor for RA development was old-age at onset (P = 0.038).

Conclusion: The most common presentation of Thai UA was asymmetrical oligoarthritis and most patients had persistent arthritis correlated with hyperglobulinemia. Elderly-onset, without any radiographic changes or rheumatoid factor, was predictive of RA development during follow-up.