Other seronegative spondyloarthropathies

Seronegative spondyloarthropathies are a group of overlapping forms of inflammatory joint disease, the most common conditions being ankylosing spondylitis and psoriatic arthritis. Other less common conditions include reactive arthritis, enteropathic arthritis and SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis). Shared features include a propensity to affect the spine, an association with anterior uveitis, involvement of the enthesis, the absence of rheumatoid factor and an increased frequency of HLA-B27. Psoriatic arthritis has several distinctive characteristics that may vary from patient to patient and include frequent involvement of distal interphalangeal joints, dactylitis, new bone formation within the enthesis, osteolysis and ankylosis. Genetic factors are important, with HLA-CW6-containing haplotypes associated with psoriasis and peripheral joint inflammation, and HLA-B27 associated with axial involvement, especially sacroiliitis. The advent of tumour necrosis factor-α inhibitors provides an important new dimension to treatment options for those with severe or persistently active disease.