RESUMEN
Vitamin D deficiency has been described in SLE and OA. Low vitamin D level is prevalent in Egyptian SLE patients while controversial studies are present regarding its level in OA patients in Egypt. We investigated whether vitamin D receptor (VDR) genes Bsm1 and Fok1 polymorphisms could be used as genetic markers for the susceptibility to SLE and /or OA in a sample of Egyptian population. The study was carried out on 100 SLE patients, 100 osteoarthritic patients and 100 normal controls using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Our results showed a statistically significant difference in Fok1 genotype distribution between SLE and OA patients (p=0.001). In SLE group, the "f" allele was significantly over-represented where 30% had "f" allele compared to 0% in OA (P = 0.03). Fok1 ff genotypes showed a significant association with disease activity in SLE patients. In addition, the fb haplotype frequency was significantly higher in SLE patients than controls (P=0.01). In conclusion Fok1 genotype and f allelic frequencies may be susceptible risk factors for SLE rather than OA in Egyptian patients.