Spondyloarthropathies

The spondyloarthropathies are a family of interrelated, seronegative inflammatory arthritides that share a tendency to involve the axial skeleton and entheses, an association with the HLA-B27 allele, and overlapping extra-articular features such as uveitis, psoriasis, and inflammatory bowel disease. They include axial spondyloarthritis (with ankylosing spondylitis), psoriatic arthritis, reactive arthritis, and enteropathic arthritis.

Definition

The spondyloarthropathies are a group of chronic seronegative inflammatory rheumatic diseases characterised by inflammation of the axial skeleton and entheses, an association with HLA-B27, and shared extra-articular manifestations, encompassing axial spondyloarthritis, psoriatic arthritis, reactive arthritis, and arthritis associated with inflammatory bowel disease.

Scope

This topic introduces the spondyloarthropathies as a unifying disease concept, covering their shared clinical and genetic features, the axial and peripheral patterns, and the classification frameworks (modified New York and ASAS criteria) used to identify them. It is a clinical-entity reference entry and does not provide individualised diagnostic or treatment guidance.

Core questions

• What clinical and genetic features unify the spondyloarthropathies as a single family?
• How do axial and peripheral patterns of spondyloarthritis differ?
• How do the ASAS and modified New York criteria classify these conditions?

Key concepts

• Enthesitis
• Axial versus peripheral spondyloarthritis
• HLA-B27 association
• Inflammatory back pain and sacroiliitis
• Seronegativity (absence of rheumatoid factor)
• Extra-articular features (uveitis, psoriasis, IBD)
• ASAS and modified New York classification

Mechanisms

The spondyloarthropathies are characterised by inflammation centred on the enthesis — the site where tendons and ligaments insert into bone — and on the sacroiliac joints and spine. A strong genetic predisposition, most notably the HLA-B27 allele, interacts with innate immune pathways and, in some forms, with gut or skin inflammation. Unlike the predominantly erosive process of rheumatoid arthritis, spondyloarthritis can drive both bone erosion and pathological new bone formation, leading over time to spinal ankylosis in susceptible individuals.

Clinical relevance

Spondyloarthropathy is suggested by inflammatory back pain, asymmetric large-joint or peripheral arthritis, enthesitis, dactylitis, and extra-articular features, supported by HLA-B27 testing and imaging of the sacroiliac joints. Classification uses the ASAS criteria for axial and peripheral disease and the modified New York criteria for established ankylosing spondylitis. This entry describes the disease concept and classification and is not a basis for individual clinical decisions.

Epidemiology

As a group the spondyloarthropathies have an estimated prevalence broadly comparable to that of rheumatoid arthritis, with axial spondyloarthritis showing a male predominance in its ankylosing form and onset typically in early adulthood. Prevalence tracks with the population frequency of HLA-B27, which varies markedly by geography and ancestry.

Evidence & guidelines

Classification of the spondyloarthropathies is anchored by the ASAS criteria for axial and peripheral spondyloarthritis and by the modified New York criteria for ankylosing spondylitis, while disease-specific recommendation sets, such as the GRAPPA recommendations for psoriatic arthritis, summarise the management evidence base at a population level.

History

The concept of the spondyloarthropathies coalesced in the 1970s, when researchers recognised that ankylosing spondylitis, reactive arthritis, psoriatic arthritis, and enteropathic arthritis shared seronegativity, axial involvement, and a striking association with the newly described HLA-B27 antigen. The modified New York criteria (1984) standardised the diagnosis of ankylosing spondylitis, and the later ASAS criteria broadened the framework to capture earlier, non-radiographic axial disease.

Debates

Is non-radiographic axial spondyloarthritis a distinct entity or an early phase of ankylosing spondylitis?

The ASAS criteria captured patients with axial inflammation lacking definite radiographic sacroiliitis; whether non-radiographic axial spondyloarthritis is best understood as early ankylosing spondylitis or as a partly separate condition with its own progression risk remains discussed.

Key figures

• Joachim Sieper
• Martin Rudwaleit
• Desiree van der Heijde
• Sjef van der Linden
• Joel Taurog

Seminal works

• vanderlinden-1984
• rudwaleit-2009
• taurog-2016
• coates-2016-grappa

Frequently asked questions

Why are the spondyloarthropathies called 'seronegative'?

They typically lack rheumatoid factor and anti-citrullinated protein antibodies, which distinguishes them serologically from rheumatoid arthritis even when peripheral joints are involved.

What role does HLA-B27 play in these conditions?

HLA-B27 is strongly associated with several spondyloarthropathies, especially ankylosing spondylitis, and supports classification, but it is neither necessary nor sufficient for diagnosis since many carriers never develop disease.