Vitamin D Receptor Gene Polymorphism ApaI As a Predisposing Factor for Psoriasis and Its Relation With Serum Vitamin D Levels and Psoriasis Severity

Background And Aim: Psoriasis is a chronic, relapsing and inflammatory multisystemic disease with both genetic predisposition and autoimmune pathogenic traits. Several types of vitamin D receptor (VDR) polymorphisms have been investigated as a predisposing factor for psoriasis susceptibility with controversial results. However, the exact pathophysiological effect of the VDR gene on psoriasis susceptibility remains poorly understood. We aimed to determine whether VDR gene polymorphisms, specifically rs7975232 (ApaI), afford psoriasis susceptibility in a given community in Saudi Arabia. Also, to assess its possible relation with disease severity.

Subjects And Methods: In a comparative case-control study comprising 53 psoriatic patients and 41 matched healthy controls, we measured serum ApaI levels, and the PCR-RFLEP technique detected ApaI genetic polymorphism (rs7975232) for both groups. Serum vitamin D level was measured in both groups.

Result: Our results revealed that A/A genotype of ApaI was significantly more predominant in patients than controls, while A/a genotype was more common in healthy subjects. Furthermore, A allele was significantly over-represented in the patients' group compared to the controls (P≤0.001). Serum vitamin D levels were significantly higher in mild psoriatic patients than in those with moderate and severe types (P=0.002). Mild psoriatic patients with a/a genotypes have higher vitamin D levels than severe patients with A/A genotypes and A/a moderate patients (P≤0.001).

Conclusion: Our data indicated clearly that VDR gene polymorphism, namely ApaI, is associated with psoriasis susceptibility. Furthermore, serum vitamin D level in psoriatic patients varies among different ApaI genotypes, where it is lowest in AA genotype.