Deoxyribonuclease I (DNASE1) may be responsible for the removal of DNA from nuclear antigens at sites of high cell turnover, thus preventing the onset of systemic lupus erythematosus (SLE). The purpose of this study was to screen DNASE1 gene for mutations that may have an effect on susceptibility to develop SLE. DNA was extracted from 76 Kuwaiti SLE patients and 92 race-matched controls. PCR-direct sequencing was used to screen DNASE1 promoter, coding sequence and exon-intron boundaries for mutation. Association of genomic variations was assessed using a Chi-square test. Molecular analysis of the DNASE1 gene did not reveal any mutation. However, a 56-bp repeat was detected in intron4 which was previously reported and named HumDN1. The allelic and genotypic distributions of the HumDN1 VNTR were compared between SLE patients and healthy subjects. Alleles were denoted as 2, 3, 4, 5 and 6 corresponding to the number of repeats of the 56 bp unit. Alleles 4, 5, and 6 showed significant association with SLE. Allele 5 showed the highest association [chi(2) = 32.57; P < or = 0.001; OR = 4.16; 95% CI: (2.55-6.79)]. Association of allele 5 was also found at the genotypic level, where genotype 5/5 is more prevalent in SLE subjects as compared with controls (17% versus 9%). We report a significant association of HumDN1 VNTR polymorphism in DNASE1 gene with SLE. Further functional assays needed to assess the effect of this VNTR on DNASE1 activity and its association with SLE.