Polymorphism of the vitamin D₃ receptor in patients with psoriasis

Abstract

1,25-Dihydroxyvitamin D is the biologically active form of vitamin D for the treatment of skin eruptions in patients with psoriasis. 1,25-(OH)₂D₃ elicits its action on skin eruptions through the vitamin D receptor (VDR). Allelic frequencies of VDR were studied in 86 normal subjects and 50 patients with psoriasis. Genomic DNA was extracted from peripheral blood leukocytes and the VDR gene was amplified using a heminested polymerase chain reaction (PCR). The products were digested with respective restriction enzymes ApaI, TaqI and BsmI. The restriction fragment length polymorphisms (RFLP) were coded as Aa, Tt or Bb. The frequencies of ApaI, BsmI and TaqI RFLP genotypes in psoriasis patients showed no significant differences compared with normal controls. The frequency of the AA genotype was significantly higher in pustulosis palmaris et plantaris patients than in psoriasis vulgaris patients (P<0.05), and in psoriasis vulgaris patients than in psoriasis pustulosa patients (P<0.01). In patients with psoriasis, the levels of serum alanine 2-oxoglutarate aminotransferase (ALT) were significantly higher in patients with the AA genotype (54.0±22.0 IU/l, n=4) than in those with the aa genotype (24.0±15.9 IU/l, n=27; P<0.02). The distribution of ApaI, BsmI, TaqI RFLP VDR genotypes showed no significant relationship to the PASI score, serum aspartate 2-oxoglutarate aminotransferase or triglyceride levels, or age at onset. These results show that the VDR genotype contributes to the liver dysfunction in patients with psoriasis, although no correlation was found between VDR genotype and the skin eruptions of psoriasis.