By Ingrid Grasmo
Polymorphisms in the vitamin D receptor (VDR) gene may be involved in the etiology of vitiligo, suggest study findings from a population of Chinese individuals.
"Genetic variations within the VDR gene could lead to significant receptor dysfunction, as polymorphisms in the VDR have been found to be associated with many autoimmune diseases, including vitiligo," say Tianwen Gao (Fourth Medical University, Shaanxi, China) and colleagues.
Indeed, current treatments for vitiligo include topical vitamin D analogs which appear to be effective.
The researchers investigated four VDR gene alleles - FokI, BsmI, ApaI, and TaqI - among 749 patients with vitiligo and 763 matched individuals without the condition. Levels of 25(OH)D were also measured to evaluate possible associations between the VDR polymorphic variants and findings of vitiligo.
Genotype distribution of VDR polymorphisms revealed that the BsmI variant B, ApaI variant A, and TaqI variant t allele frequencies were significantly lower among patients with vitiligo compared with controls.
Compared with the BsmI bb genotype, patients with the Bb genotype had a significant 28% decreased risk for vitiligo, patients with the ApaI Aa and AA genotypes had respective 23% and 45% reduced risks relative to those with the aa genotype, and those with TaqI Tt genotype had a 30% decreased risk relative to patients with the TT genotype.
Regression analysis revealed that 25(OH)D levels above 18.72 ng/mL were significantly associated with a 54% reduced risk for vitiligo compared with levels below this cutoff. On stratification by 25(OH)D levels, patients in the highest (23.80 ng/mL or over) and mid (14.95-23.80 ng/mL) tertiles of 25(OH)D showed a 64% and 45% reduced risk for vitiligo compared with patients showing levels below 14.95 ng/mL.
The Fok1 allele was found to be a significant predictor for 25(OH)D levels in vitiligo patients and controls, while the ApaI allele was a significant predictor only among vitiligo patients.
Lastly, the researchers found that the Aa and AA ApaI genotypes in combination with higher 25(OH)D levels were associated with a 64% (for 14.95-23.80 ng/mL) and 69% (for over 23.80 ng/mL) reduced risk for vitiligo.
Writing in the British Journal of Dermatology, the researchers say the results suggest "that VDR polymorphisms may affect VDR function and the risk for developing vitiligo in the Chinese population."
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