Prevalence, disease manifestations, and treatment of psoriatic arthritis in Western Norway.

Objective: To estimate the prevalence of psoriatic arthritis (PsA) in a geographically defined population, and to characterize the clinical manifestations and medical treatment for PsA.
Methods: Prevalent cases were identified for the years 1999-2002 at the rheumatology centers for the population of 442,000 inhabitants. Clinical data were extracted from patient records. Cases with psoriasis and peripheral arthritis and/or radiographic evidence of spondyloarthritis were considered to have PsA, those with other arthritides were excluded.
Results: In total, 634 patients with PsA were identified from the adult population, equivalent to a prevalence of 1.95 per 1000 (1.80-2.10). There were no significant sex differences in rates; for both sexes the prevalence was highest in the age group 40 to 59 years. Polyarthritis was the most frequent subclass (68.6%). Oligoarthritis, monoarthritis, and arthritis confined to the spine or sacroiliac joints were seen in 22.9%, 5.8%, and 2.7% of cases, respectively. Mean age was higher (50.6 yrs for all cases), and mean disease duration was longer (10.7 yrs) with increasing number of joints affected. The mean erythrocyte sedimentation rate and C-reactive protein were higher with increasing number of joints affected and disease duration. Intraarticular injection of glucocorticoids had been administered to 40.0% of the patients during the last year. Disease modifying antirheumatic drugs were used by 40.0%, with oral methotrexate being the most frequently used.
Conclusion: The estimated prevalence of PsA was 1.95 per 1000 adult inhabitants, which is higher than previously reported. The demographic data support the presence of a shift from mono- and oligoarthritis to polyarthritis and increased inflammatory activity with increasing disease duration. Methotrexate and intraarticular glucocorticoids were frequently used treatments.