Diffuse Idiopathic Skeletal Hyperostosis in Psoriatic Arthritis

Objective. To determine the prevalence of diffuse idiopathic skeletal hyperostosis (DISH) in patients with psoriatic arthritis (PsA) and to identify the features associated with its occurrence. Methods. Patients were recruited from the University of Toronto PsA observational cohort initiated in 1978. All patients fulfilled the CASPAR criteria. Radiographs of peripheral joints and spine were obtained every 2 years. DISH was defined as flowing bony bridges in at least 4 contiguous thoracic vertebrae. Each PsA patient with DISH was matched by sex to 3 PsA patients without DISH. Demographics, disease characteristics, and radiographic features were compared using McNemar test, Fisher's exact test, chi-square test, and paired t test as appropriate. Logistic regression analyses models with stepwise regression were conducted. Results. DISH was observed in 78 (8.3%) of 938 patients with PsA. Patients with DISH were older and had longer disease duration, higher body mass index (BMI), and higher uric acid levels. Diabetes and hypertension were more prevalent in patients with DISH than in those without. The severity of radiographic damage to peripheral joints was also greater in patients with DISH. The presence of inflammatory back pain, HLA-B*27 allele, and sacroiliitis was similar in both groups. Patients with DISH had more syndesmophytes and calcaneal spurs. Older age, higher BMI, and the presence of radiographic damage to peripheral joints were associated with DISH in multivariate analysis. Conclusion. The diagnosis of DISH is possible in the presence of axial PsA. DISH was associated with known DISH-related factors including older age and high BMI, as well as the presence of radiographic damage to peripheral joints.