The general signs include dwarfism, baldness, a pinched nose, small face and jaw relative to head size, delayed tooth formation, aged skin, stiff joints, hip dislocations, generalized atherosclerosis, and cardiovascular problems. The children have a remarkably similar appearance despite racial background, and they tend to have above-average intelligence.
The condition is caused by a single misplaced DNA molecule within the human genome that contains some three billion DNA units. The gene was discovered in April 2003 by researchers at the National Human Genome Research Institute. The mutation on a gene called lamin A on chromosome 1 was found in DNA specimens from 18 of 20 progeria patients. A similar study found the gene mutation in two progeria patients. The flaw is a substitution of a single DNA base, when the amino acid guanine is switched to adenine. Lamin A, or LMNA, has already been linked to six other diseases, but the mutation and its effect are slightly different, on a molecular basis, in each of the diseases.
Brothers, sisters, and nonidentical twins are almost never affected in the same family, and the average difference in ages between father and mother is about six years as compared with the national average of about two years. Researchers now believe that progeria is not genetically inherited but develops spontaneously in each patient, although it could be that the mutant progeria gene is transferred to the embryo through a flaw in the genes of the father's sperm. Researchers are now going to study people who live to be very old see if some element of their LMNA gene makes them resistant to the diseases of aging.
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