Undifferentiated spondyloarthritis (uSpA), also known as undifferentiated arthritis, is a non-specific mono- or polyarthropathy that lacks the clinical, serological and radiological features that would allow specific diagnosis. It often turns out to be an early presentation of a more well known form of arthritis.
The prevalence of uSpA is estimated at ~1% 4.
Back pain, enthesitis, peripheral arthritis are common, as well as extra-skeletal manifestations such as dactylitis and fatigue 1.
Depends on the underlying cause. Most cases reveal themselves to be either:
- rheumatoid arthritis
- seronegative spondyloarthropathy
- degenerative joint disease
- HLA B27 positive in ~75% (range 70-84%) 4
Only 50% of presentations have abnormal levels of acute phase reactants (CRP, ESR) and only 10% are positive for rheumatoid factor despite many eventually declaring themselves as rheumatoid arthritis 3.
Treatment and prognosis
A specific diagnosis is usually reached within three months:
- 1. Thabet MM, Huizinga TW, van der Heijde DM, van der Helm-van Mil AH. "The prognostic value of baseline erosions in undifferentiated arthritis. Arthritis Res Ther." 2009;11(5):R155. Epub 2009 Oct 15.
- 2. Lukas C, Combe B, Ravaud P, Sibilia J, Landew R, van der Heijde D. "Favorable effect of very early disease-modifying antirheumatic drug treatment on radiographic progression in early inflammatory arthritis: Data from theÉtude et Suivi des polyarthrites indifférenciées récentes (study and followup of early undifferentiated polyarthritis)." Arthritis Rheum. 2011 Jul;63(7):1804-11.
- 3. Krabben A, Huizinga TW, van der Helm-van Mil AH. Undifferentiated arthritis characteristics and outcomes when applying the 2010 and 1987 criteria for rheumatoid arthritis. Ann. Rheum. Dis. 2011;71 (2): 238-41. doi:10.1136/annrheumdis-2011-200205 - Pubmed citation
- 4. Zochling J, Brandt J, Braun J. The current concept of spondyloarthritis with special emphasis on undifferentiated spondyloarthritis. Rheumatology (Oxford). 2005;44 (12): 1483-91. doi:10.1093/rheumatology/kei047 - Pubmed citation
- 5. Paramarta JE, De Rycke L, Ambarus CA et-al. Undifferentiated spondyloarthritis vs ankylosing spondylitis and psoriatic arthritis: a real-life prospective cohort study of clinical presentation and response to treatment. Rheumatology (Oxford). 2013;52 (10): 1873-8. doi:10.1093/rheumatology/ket239 - Pubmed citation