Anatomic, metabolic, neuropsychological, and molecular genetic studies of three pairs of identical twins discordant for dementia of the Alzheimer's type
A. Kumar, M. B. Schapiro, C. L. Grady, M. F. Matocha, J. V. Haxby, A. M. Moore, J. S. Luxenberg, P. H. St George-Hyslop, C. D. Robinette, M. J. Ball and al. et
Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Md. 20892.
Three pairs of twins, each with proved monozygosity, were shown to be
discordant for dementia of the Alzheimer's type and to have remained
discordant for periods of 8 to 11 years. Dementia of the Alzheimer's type
was demonstrated by history; serial clinical examinations; serial
measurements of cerebral glucose utilization using positron emission
tomography and of cerebral ventricular volumes and of rates of change of
volumes using quantitative computed tomography; and by serial
neuropsychological tests. The results of each of these measures showed no
evidence of clinical abnormality in any unaffected twin. DNA markers from
the proximal long arm of chromosome 21 did not distinguish between the
affected and the unaffected member of any pair of identical twins. Family
pedigrees were negative for Alzheimer's disease. The results suggest that
environmental or other nongenetic factors contribute to Alzheimer's disease
in discordant monozygotic twins, or that some cases arise by a postzygotic
somatic mutation.
