Relationship of psoriatic arthritis with the other spondyloarthropathies

Purpose of review The seronegative spondyloarthropathies are a group of disorders sharing common clinical features, the hallmark of which is sacroiliitis. Despite the 40 years since psoriatic arthritis was recognized, controversy still exists about which patients to include within this disease group and the relation of psoriatic arthritis with the other spondyloarthropathies. Recent findings Early disease can present difficulties because it is inappropriate to use criteria developed on established cases in early arthritis, in which many cases may be initially undifferentiated. The taxonomy of juvenile spondyloarthropathy remains a contentious issue, and further modifications of the Durban criteria have been suggested. The predictive value of the European Spondyloarthropathy Study Group criteria for spondyloarthropathy varies with the prevalence of the disease in the population under consideration, as has been demonstrated in ambulatory practice in France and Spain. It appears that physicians differ in their interpretation of the individual features, particularly of such clinical items as asymmetry and predominantly lower limb involvement. The combination of dactylitis of a toe, heel pain, and oligoarthritis appears to be strongly suggestive of psoriatic arthritis. However, solitary heel pain can be problematic, and ultrasonographic entheseal erosion at the calcaneum has been shown equally in rheumatoid arthritis and psoriatic arthritis. MRI may be more sensitive and quantitatively discriminative in psoriatic arthritis. Spinal involvement in psoriatic arthritis can be asymptomatic, as in classical ankylosing spondylitis. Importantly, psoriatic spondylitis has been observed in the absence of sacroiliitis. Summary Clinicians generally agree that psoriatic arthritis constitutes a discreet subset within the spondyloarthropathy group, but the demarcation continues to be the subject of clinical research. The matter is confounded by the lack of agreed classification criteria for psoriatic arthritis; although in both adult and juvenile disease criteria for spondyloarthropathy exist, the place of psoriatic arthritis within this larger group requires further definition.