Serum concentrations of 25-OH vitamin D and the pro-inflammatory interleukins IL-17, IL-23, and IL-18 in patients with plaque psoriasis.

Aims: The present study aimed to assess vitamin D status and serum concentrations of pro-inflammatory cytokines IL-17, Il-23, and IL-18 in patients with chronic plaque psoriasis and their association with various demographic and clinical characteristics.

Methods: The study was conducted during the autumn/winter period on 48 patients with chronic plaque psoriasis and 48 controls. Total serum 25(OH)D level was determined with Roche Elecsys^® 2010 Vitamin D total assay. Commercial ELISA kits were used for quantifying the serum levels of IL-17A, IL-18, and IL-23.

Results: Serum 25(OH)D had a median value of 16.95 ng/mL (IQR 10.8-23.50) for patients with psoriasis and 18.80 ng/mL (IQR 15.45-25.85) for the control group (P=0.09). A moderate negative correlation was found between PASI score and 25(OH)D levels (r_s=-0.34; P=0.02). The serum levels of IL-17 (P=0.001), IL-23 (P=0.01) and IL-18 (P=0.02) were significantly higher in the patient group compared to controls. IL-17 concentrations were higher in patients with moderate to severe psoriasis compared to patients with mild psoriasis (P=0.003). No significant correlations were detected between the serum concentrations of 25(ОH)D and IL-17, IL-23, and IL-18.

Conclusion: It was confirmed that IL-17 serum level is associated with psoriasis severity. Measurement of 25(OH)D serum concentration can be useful in patients with moderate to severe psoriasis with or without comorbidities. A direct association between 25(OH)D serum concentration and the serum concentrations of IL-17, IL-23, or IL-18 was not identified in this study.