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E.A. Postel, A. Agarwal, Y.–T. Fan, S. Schmidt, J. Caldwell, R. Domurath, W. Scott, J. Haines, M. Pericak–Vance; Comparison of phenotype in singleton and multiplex AMD . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2722.
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Purpose: Age–related macular degeneration (AMD) is a common cause of irreversible blindness in the elderly, caused by a complex interaction of genes and the environment. As part of our genetic epidemiological studies of AMD, we compared 536 singleton and multiplex AMD probands, to determine if they shared a similar or different phenotype. Methods: Data were analyzed from 125 multiplex and 411 singleton probands with at least grade 3 AMD. Complete ocular examinations were performed. Grading was based on an accepted classification scheme, using color 35mm photographs. Results: No statistically significant difference was found between the singleton and multiplex groups with respect to distribution of grade; grade variability; the presence of small, intermediate, or large drusen; retinal pigment hyper– or hypopigmentation; peripheral reticular pigmentary change; type or extent of cataract; sex; and body–mass index. Significant differences were noted in iris color (p=0.03); the presence of geographic atrophy (in the presence of grade 5 disease) (p=0.02) and peripheral drusen (p=0.0001); and lens status (p=0.0007). None of these differences had an effect on grade in multivariate logistic regression analysis. A significant difference was noted between the two groups with respect to age (73.9 years for multiplex probands, 76.6 years for singleton) (p=0.03). However, when multiplex and singleton probands of the same grade were compared, no age difference was found. Conclusions:Singleton and multiplex probands shared a similar distribution of grades and other features typical of AMD. This has important implications for the study of this complex disease, suggesting that the combined population may be used in candidate gene and other studies. In addition, this analysis suggests that reporting of family history in this late–onset, often mildly symptomatic disease may be inaccurate.
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