PURPOSE: To investigate the lysyl oxidase-like 1 (LOXL1) gene for single nucleotide polymorphism (SNP) variations in Japanese patients with exfoliation syndrome (XFS) and exfoliation glaucoma (XFG) and to examine the phenotypes of the patients with these variations. METHODS: Fifty-six unrelated Japanese patients with XFS, including 36 patients with XFG, were studied. Genomic DNA was extracted from the leukocytes of peripheral blood, and three SNPs (rs1048661; p.Arg141Leu, rs3825942; p.Gly153Asp, and rs2165241) were identified. These SNPs were amplified by polymerase chain reaction (PCR), directly sequenced, and genotyped. RESULTS: Two nonsynonymous variants in exon 1 of LOXL1,rs1048661 and rs3825942, were found to be strongly associated with XFS including XFG. The frequency of the T allele (0.964) in rs1048661 in eyes with XFS was much higher in controls (0.507) with a p value of 7.7x10(-18). The odds ratio for the T allele in rs1048661 was 26.0 (95% confidence interval, 18.3-37.1). In the haplotype analysis, T-G was overrepresented in XFS subjects (p=7.7x10(-18)), showing a highly significant difference in frequency between primary open-angle glaucoma (POAG) and the control group (p=0.07), but the G-G and G-A haplotypes were less represented in XFS subjects (p=1.1x10(-11) and p=1.0x10(-4), respectively). However, an earlier study reported the strongest associated SNP with XFS and XFG, rs2165241, showed no association. CONCLUSIONS: SNPs of LOXL1 (rs1048661; Arg141Leu and rs3825942; Gly153Asp) are highly associated with XFS in the Japanese population. However, unidentified genetic or environmental factors independent of LOXL1 will most likely influence the phenotypic expression of the syndrome.