
Background: Patients with sickle cell disease (SCD) had a low serum level of vitamin D. Also, genotypic analysis in Bahraini SCD patient has not been investigated. Aim: To investigate gene polymorphisms (SNP) and to observe if genotyping, allelic discrimination or allele frequency have any effects on SCD patients compared to controls. Methods: For quantification of serum PTH, ELISA kits were used. Calcium (Ca), phosphate (Ph) and Alkaline Phosphatase (ALP) were measured using the auto analyzer (Cobas). Gene polymorphisms of VDR and PTH genes were investigated using real-time PCR. Results: Genotypic analysis in the VDR gene revealed complete absence of homozygous allele A (the mutant allele) among both SC patients and controls. AG genotypes was more frequent than the GG genotypes in patient and controls (p<0.012). The percentage of allele A frequency was 61.4% and 66.1% within patient and controls, respectively with no statistical difference. Yet, the analysis showed no association within sex between genotypes and allele’s frequency. In the PTH gene, the GG-genotype was more frequent than the AG genotype in patients and controls (p<0.022). The percentage of A allele was 34.3% in patients and 25.8% in controls, but the difference was not significant. No association was found between GG genotype in sex and allele frequency and sex in PTH gene. Conclusion: In the VDR gene the AG genotype is associated with SCD, while in PTH gene the GG genotype is associated with SCD. There was no statistical difference in allele’s frequencies between patients and controls in both VDR and PTH genes. Moreover, no association was found between VDR and PTH gene polymorphisms and their corresponding serum levels suggesting that allele A may be associated with vitamin D serum level.