Association of a vitamin D receptor gene polymorphism with localized early-onset periodontal diseases

Background: Early-onset periodontal diseases (EOP) are caused by interactio ns between host factors, specific microbial pathogens, and environmental fa ctors. It is, therefore, of interest to investigate the nature of host fact ors as they may provide useful risk markers and reveal important informatio n regarding the disease pathogenesis, Genetic polymorphisms in the vitamin D receptor (VDR) gene are associated with parameters of bone homeostasis an d with diseases in which bone loss is a cardinal sign, in particular osteop orosis. Rapidly progressive bone loss is one feature of EOP. We, therefore, sought to determine whether EOP is associated with a polymorphism in the V DR gene. Methods: A restriction fragment length polymorphism (RFLP) for Tag I in exo n nine of the VDR gene was analyzed by PCR, followed by restriction digesti on with Tag I and gel electrophoresis. We analyzed the genotypes of 69 EOP patients, including 20 patients with unequivocal evidence of localized dise ase (L-EOP), and 72 controls with no history of EOP. Results: The genotype distribution in the L-EOP patient group was 7 (35%), 5 (25%) and 8 (40%) and in the control group 31 (43.1%), 36 (50.0%) and 5 ( 6.9%) for TT, Tt and tt respectively (where t and T represent the alleles w ith and without the Tag I RFLP respectively). chi(2) analysis indicated tha t the distribution of the genotypes between these two groups was highly sig nificantly different (P = 0.001). Allele frequencies were 47.5% and 52.5% f or T and t in the L-EOP group; 68.1% and 31.9% in the control group, showin g a significant association between the prevalence of the less frequent all ele (t) and L-EOP (P = 0.017). There was no significant difference in the g enotype distribution or the allele frequencies between the control samples and the larger EOP patient group (n = 69) which included patients with gene ralized and localized disease. Conclusions: These data indicate that carriage of the less frequent allele of the Tag I RFLP (t) in the VDR gene significantly increases the risk of d eveloping L-EOP, However, VDR genotype may not affect the incidence of all cases of EOP. These findings contribute to our understanding of the genetic basis for periodontal disease and may help define sub-groups of this disea se which share common pathogenic factors.