Psoriasis is a systemic, immune-mediated disease characterized by inflammatory manifestations in the skin and joints. Vitamin D deficiency is currently considered a pandemic and is associated with comorbidities including psoriasis and psoriatic arthritis (PsA). To determine the prevalence of hypovitaminosis D [25(OH)D] in patients with plaque psoriasis, with and without PsA, and of independent predictors of serum 25(OH)D levels. Retrospective cross-sectional study conducted among 300 patients at an outpatient clinic in a university center in Juiz de Fora, Minas Gerais, Brazil. Demographic and clinical data (psoriasis area and severity index [PASI], family history, age at onset, disease duration, and the presence of PsA according to Classification Criteria for Psoriatic Arthritis), skin phototype, and season of the year were reviewed. Hypovitaminosis D (< 30 ng/mL) was highly prevalent in patients with psoriasis with and without PsA (82.2% and 74.9%, respectively). An inverse correlation between PASI and vitamin D was found (without PsA r = –0.59 and, PsA r = –0.52, P < 0.001), and multivariate regression revealed that hypovitaminosis D was associated with disease severity, season, and phototype. It was confirmed by binary logistic regression between PASI and vitamin D deficiency (< 30 ng/mL), (odds ratio, OR 1.78 CI: –0.20–0.53, P < 0.001). Hypovitaminosis D (< 30 ng/mL) was highly prevalent in psoriatic patients with and without PsA. Season and skin phototype were associated with 25(OH)D levels. An inverse association between PASI and serum 25(OH)D levels was established.

BACKGROUND: Psoriatic arthritis is the most frequent and impactful comorbidity among psoriatic patients and appears in most cases after skin disease. Dermatologists play a key role in its early diagnosis and treatment. OBJECTIVES: To determine the prevalence of psoriatic arthritis and associated variables among patients wit h plaque psoriasis seen at a reference center for treating psoriasis. DESIGN AND SETTING: Retrospective cross-sectional study conducted among 300 patients at an outpatient clinic in a university center in Juiz de Fora, MG, Brazil. METHODS: Standardized records of 300 patients with plaque psoriasis were examined. Demographic data and medical variables relating to psoriasis (Psoriasis Area and Severity Index (PASI), family history, age at onset and disease progression) and psoriasis arthritis (CASPAR criteria) were evaluated. Laboratory and radiographic tests in the medical records were reviewed. RESULTS: Seventy-three (243%) of these 300 patients with plaque psoriasis had psoriatic arthritis. Asymmetric oligoarthritis (58.9%) was the most common clinical form, followed by polyarthritis (205%), distal interphalangeal arthritis (15.2%) and spondyloarthritis (5.4%). Dactylitis was present in 21.9% and enthesitis in 35.6% of patients. Compared with patients without arthritis, patients with arthritis had higher average age, higher frequency of positive family history of psoriasis, longer duration of evolution and higher PASI rates. CONCLUSION: Psoriatic arthritis is often underdiagnosed. Since dermatologists perform the initial approach, these professionals need to be trained to diagnose this comorbidity and treat it, together with rheumatologists.