Vitamin D receptor gene polymorphism and growth pattern in Egyptian rachitic children

Nutritional rickets may be caused by either calcium or vitamin D deficiency. Vitamin D affects skeletal metabolism indirectly. The association between Vitamin D receptor (VDR) gene polymorphisms and genetic and environmental factors plays a role in the majority of cases. Several studies reported association between rickets and VDR gene polymorphism and growth parameters. Vitamin D affects skeletal metabolism by regulating calcium and phosphate homeostasis. The aim of this study was to examine the association between VDR gene polymorphism and vitamin D deficiency in Egyptian children with rickets and assess the relationship between the VDR gene polymorphisms and growth parameters. The study included 42 (16 girls and 26 boys) patients recruited from ALZharaa hospital, AL-Azhar University. Their age ranged from 4-36 months. Forty eight healthy individuals matched in age and sex with patients was recruited for comparison.VDR gene ApaI, FokI, and TaqI polymorphisms, biochemical and growth parameters were studied. Results showed that the most common VDR genotype was Ff among patients and Aa among controls, with no significant differences. The allele frequency showed significant increase in the "f" (FokI) allele in patients compared to controls (33.3% vs 20.8%, P=0.04). While, there were no significant differences between patients and controls in frequency of TaqI and ApaI alleles. The frequencies of combinations of VDR genotypes for the FokI, ApaI, and TaqI polymorphic sites, were significantly different between rachitic and control subjects (p <0.01). The AaFfTT genotype was the most frequent one among the rachitic group, while the AaFFTT is the most predominant in the control group. The FF and tt genotypes were associated with reduced SDS of weight and height. This denotes that the VDR polymorphism has functional significance on growth parameters. In conclusions, the study shows that there is a relation between VDR gene polymorphisms and susceptibility to rickets. These results might help in risk assessment of rickets and in predicting response to treatment.