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Heredity and age-related macular degeneration. Observations in monozygotic twins
M L Klein1, W M Mauldin, V D Stoumbos
1Casey Eye Institute, Oregon Health Sciences University, Portland.
Objective:
To determine the concordance of age-related macular degenerative changes in monozygotic twins.
Patients:
Between 1984 and 1993, we examined a total of nine pairs of monozygotic twins with substantial age-related macular degenerative changes in at least one member of the pair, ranging from extensive large drusen to advanced atrophic and/or disciform scarring. Eight pairs were female and one pair was male. Ages ranged from 62 to 88 years. Monozygosity was confirmed by genetic testing in each of the seven twin pairs on whom it was performed.
Results:
In eight of the nine twin pairs, the fundus appearance and the incidence of visual impairment were similar. In the ninth pair, one twin had advanced exudative age-related macular degeneration with vision loss in one eye, while the other had large, confluent drusen and good visual function in both eyes. Environmental factor, including diet, geographic background, and medical history, were essentially similar in the twin pairs.
Conclusion:
Although selection factors and similar environmental influences might impact our findings, the markedly similar incidence of macular degenerative changes in these monozygotic twins suggests that a substantial genetic component may exist in a potentially large proportion of patients with age-related macular degeneration. Further studies are warranted to define this hereditary influence.