Spondylarthropathy

Overview

The spondyloarthropathies are a diverse group of inflammatory arthritides that share certain genetic predisposing factors and clinical features. Their most characteristic feature is inflammatory back pain. Enthesitis, another characteristic feature, involves inflammation at sites where tendons, ligaments, or joint capsules attach to bone.

Features of Spondylarthropathy

Sacroiliac and spinal (axial involvement)
Enthesitis at long attachments of ligaments and tendons
Peripheral, often asymmetric, large joint inflammatory arthritis
Dactylitis (sausage digits)
Skin psoriasis

These diseases may also be accompanied by:

Asymmetric peripheral arthritis
Extra-articular disease
Uveitis

Main Spondylarthropathies

The HLA B27 molecule has an association with the spondyloarthropathies ranging between 50 and 95%. Interpretation of a positive result is complicated by the presence of this allele of the HLA B gene in up to 5–10% of the normal population.

Type	Definition	Clinical Features
Ankylosing Spondylitis (AS)	Chronic inflammatory disease primarily affecting the axial skeleton (spine, sacroiliac joints)	Inflammatory back pain, morning stiffness, reduced spinal mobility, uveitis, HLA-B27 positive
Psoriatic Arthritis (PsA)	Inflammatory arthritis associated with psoriasis	Asymmetric peripheral arthritis, dactylitis, nail pitting, enthesitis, skin plaques
Reactive Arthritis (ReA)	Sterile arthritis triggered by infection (commonly GI or GU)	Triad: arthritis, conjunctivitis, urethritis; enthesitis, keratoderma, dactylitis
Enteropathic Arthritis	Arthritis associated with inflammatory bowel disease (Crohn’s, ulcerative colitis)	Axial or peripheral arthritis, IBD symptoms, erythema nodosum, uveitis
Undifferentiated SpA	Features of SpA present but not meeting criteria for a specific subtype	Variable presentation — may have back pain, enthesitis, dactylitis, uveitis without clear subtype