Serum vitamin D level - the effect on the clinical course of psoriasis

Introduction: Psoriasis is a hyperproliferative disorder of the skin, and vitamin D analogs are widely used in its treatment. It is evident that ultraviolet radiation enables vitamin D-3 (cholecalciferol) formation in the epidermis, and this product is further converted into the active metabolites 25-hydroxycholecalciferol and 1,25-hydroxycholecalciferol, which exert several important effects on the skin. The disruption in proper functioning of the skin which occurs in psoriasis leads to a loss of capacity for cutaneous synthesis of vitamin D-3. In consequence, it activates a vicious circle that impairs homeostasis of the skin and results in a progressive decrease in the level of vitamin D in the whole human body. Aim: To estimate the prevalence of vitamin D serum deficiency in patients with psoriasis and analyse the association of vitamin D food intake with clinical features. Material and methods: Forty adults with psoriasis and 40 healthy subjects (control group) were recruited. Psoriasis plaques were diagnosed and evaluated by the PASI scale. Collected blood samples enabled measurement of serum vitamin D level by assessment with the immunoenzyme technique. Results: The analysis with the Mann-Whitney U test revealed a statistically significant difference in 25-hydroxycholecalciferol level between healthy individuals and patients with psoriasis (p = 0.048). In both groups (control and psoriatic) the level of 25-hydroxycholecalciferol was seriously deficient (< 50 nmol/l). There was also a negative correlation of 25-hydroxycholecalciferol serum level with both PASI (r = -0.43) and the duration of psoriasis (r = -0.53). Conclusions: It is necessary to bear in mind that not only the ingestion of food rich in vitamin D is necessary, but also the production of vitamin D with sun exposure. The quantity of 25-hydroxycholecalciferol is very important both in the general population and in patients with psoriasis, because these groups have a distinct metabolism.