Psoriatic arthritis in patients with psoriasis: A clinical-epidemiological study at a dermatology center in western Mexico

Background/Objective: Psoriatic arthritis (PsA) is a chronic inflammatory illness. Approximately, 15% of psoriasis patients have undiagnosed PsA. In Mexico, we found no related studies. Our objective was to investigate the clinical-epidemiological characteristics of PsA in psoriasis patients in western Mexico. Methods: A cross-sectional study including Mexican patients with clinical and histopathological diagnosis of psoriasis. Physical examination, rheumatoid factor analysis and radiographies of axial and peripheral skeleton were performed. The prevalence of PsA using the CASPAR criteria, age, sex; clinical variants of PsA, psoriasis type and the Psoriasis Area and Severity Index (PASI), were assessed. Descriptive and inferential statistics were used. Results: Of 90 patients with psoriasis, 48 met the criteria for PsA, with a prevalence of 53%, and average age of 50 +/- 15 years. Predominating were, the female sex in 29 (60%), the axial variant of PsA in 24 (50%), and psoriasis plaques in 40 (85%). The average PASI was 12 +/- 11. All cases were rheumatoid factor negative. These variables were not significantly different when comparing subjects with and without PsA, except for the female sex (60% vs. 7%; P < 0.001). Conclusions: Patients with psoriasis should intentionally be evaluated jointly Dermatologists and Rheumatologists searching joint involvement given the high prevalence of PsA previously undiagnosed.