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This five year old boy has Hutchinson-Gilford progeria, a fatal, "premature aging" disease in which children die of heart failure or stroke at an average age of thirteen. Photo courtesy of The Progeria Research Foundation, Inc. and the Barnett Family.

genetically mediated and, like other genetic disease, is not only the outcome of genetic error but might be open to clinical intervention.

Supporting this observation, there are a number of other less well-known forms of progeria, including acrogeria, metageria, and acrometage-ria, as well as several dozen human clinical syndromes and diseases with features that have been considered to have progeroid aspects. The latter category includes Wiedemann-Rautenstrauch, Donohue's, Cockayne's, Klinefelter's, Seip's, Rothmund's, Bloom's, and Turner's syndromes, ataxia telangiectasia, cervical lipodysplasia, myotonic dystrophy, dyskeratosis congenita, and trisomy 21 (Down syndrome). In each of these cases, there are features that are genetic and that have been considered segmental forms of aging.

In the most well-known of these, trisomy 21, the immune and central nervous systems both appear to senesce early, in contrast with Hutchinson-Gilford progeria, in which the opposite occurs. Bolstering the suggestion that this is a form of segmental progeria, trisomy 21 patients are prone to both infections and early onset of a form of Alzheimer's dementia.

The gene that is mutated in Werner's syndrome is known to code for a DNA helicase. This enzyme unwinds DNA for replication, transcription, recombination, and repair. The inability to repair DNA may explain the features of premature aging, as well as the increased rate of cancer in Werner's syndrome patients. Another mutated helicase is responsible for Bloom's syndrome. Both conditions are inherited as autosomal recessive disorders.

Data suggesting that Hutchinson-Gilford progeria is genetic is circumstantial. The disease is presumptively caused by a sporadic (one in eight million live births), autosomal dominant mutation, although a rare autosomal recessive mutation is not impossible. The helicase abnormality that causes Werner's syndrome is not present in Hutchinson-Gilford cells. There is a slight correlation with the paternal age at conception. Whatever the mechanism, it appears to operate prior to birth; several neonatal cases have been reported.

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