Association of the apolipoprotein E gene with age-related macular degeneration: possible effect modification by family history, age, and gender.

PURPOSE: Age-related macular degeneration (AMD) is a complex disorder affecting older adults in which genetic factors are likely to play a role. It has been previously suggested that the e4 allele of the apolipoprotein E (APOE) gene may have a protective effect on AMD risk and that the e2 allele may increase disease risk. The purpose of our study was to examine whether an independent data set would support the proposed role of APOE in AMD etiology. METHODS: We compared AMD cases (n=230) to controls (n=372) with respect to APOE genotypes using c2 tests and logistic regression analysis. We also conducted separate analyses for familial (n=129) and sporadic (n=101) AMD cases since these groups may have a different disease etiology. RESULTS: We did not find evidence for the risk-increasing effect attributed to the e2 allele in either familial or sporadic AMD. No evidence for a protective effect of the e4 allele was obtained for sporadic AMD. The age- and sex-adjusted odds ratio (OR) for e4 carriers among familial AMD cases compared to controls was 0.66 (95% confidence interval: 0.38-1.12, p=0.13). In the subgroup of individuals younger than 70 years of age, an OR of 0.24 (95% confidence interval: 0.08-0.72, p=0.004) was obtained. CONCLUSIONS: Our data modestly support a protective effect of the APOE-e4 allele on AMD risk, but emphasize the need to investigate more thoroughly whether the effect could be restricted to cases with a family history of AMD and whether it varies across age and sex groups.

Analysis of the Stargardt disease gene (ABCR) in age-related macular degeneration.

PURPOSE: Age-related macular degeneration (AMD) is a complex genetic disorder and the leading cause of severe vision loss in the elderly. The Stargardt disease gene (ABCR) has been proposed as a major genetic risk factor in AMD. The purpose of this study was to evaluate the authors' AMD population for the specific ABCR variants proposed previously as genetic risk factors for AMD. METHODS: The authors screened their AMD population (159 familial cases from 112 multiplex families and 53 sporadic cases) and 56 racially matched individuals with no known history of AMD from the same clinic population for evidence of the ABCR variants. Grading of disease severity was performed according to a standard protocol. Patients with extensive intermediate drusen or large soft drusen, drusenoid retinal pigment epithelial (RPE) detachments, geographic atrophy of the RPE, or evidence of exudative maculopathy were considered affected. Analysis for variants was performed by polymerase chain reaction amplification of individual exons of the ABCR gene with flanking primers and a combination of single-strand conformation polymorphism, heteroduplex analysis, and high-performance liquid chromatography. All abnormal conformers detected using these techniques were characterized by direct sequencing. RESULTS: The authors identified only two of the previously reported variants in their study population. Both variants occurred in sporadic cases, and none was found in familial cases or the randomly selected population. In addition, the authors identified several newly described polymorphisms and variants in both the AMD and control populations. CONCLUSIONS: Based on these initial findings, the authors suggest that ABCR is not a major genetic risk factor for AMD in their study population. Additional genetic studies are needed to more fully evaluate the role of ABCR in AMD.