TUESDAY, Feb. 26, 2002 (HealthDayNews) -- In a reproductive first, scientists say screening to detect genetic mutations in embryos has let a young woman with a rare form of early-onset Alzheimer's disease have a baby free of a gene that causes the disorder.
However, this medical achievement is spurring continued ethical debate over the possibility of creating "designer" babies. In this case especially, the doctors knew the product of their work would be a baby who will almost certainly lose her mother at an early age.
The 30-year-old mother carries a dominant gene for the degenerative brain ailment, meaning a single copy will bring on the illness. Unlike conventional Alzheimer's, which typically appears in the senior years, people with the familial form can develop dementia in their 30s. Fewer than 1 percent of all patients with the disease have the early-onset variety, which has been linked to mutations in at least three genes.
In preimplantation genetic diagnosis (PGD), scientists scan the genetic material of either a woman's egg or an early-stage embryo for the presence of known disease genes. Yury Verlinsky, director of the Reproductive Genetics Institute in Chicago, a private clinic with branches in the United States, Europe and Asia, says that by the end of this year 1,000 babies worldwide will be born through PGD. Most of these were vulnerable to inheriting more immediately disabling or fatal conditions than Alzheimer's, such as sickle cell anemia or cystic fibrosis.
The new case is the first to involve a parent with Alzheimer's disease, says Verlinsky, whose clinic performed the procedure. A report on the feat appears in tomorrow's issue of the Journal of the American Medical Association.
The case involves a woman with a strong family history of brain impairment, including a sister who developed Alzheimer's dementia at age 38. Her father, who died at 42, also suffered psychological problems and serious memory trouble. After her sister became ill, the woman was tested for a mutation linked to early-onset Alzheimer's, and was found to carry the gene, called V717L. Some of her siblings also carried the V717L error, which promotes the formation of the amyloid proteins that build up in the brain of Alzheimer's patients.
Using drugs to stimulate the woman's ovaries, the researchers tested 23 of her eggs for the presence of the Alzheimer's gene flaw. Verlinsky's group screened genetic material from eggs -- before they were fertilized -- for signs of the defect. Six of the eggs proved normal, and four were ultimately transferred into the woman. The result: a baby girl who tested free of the mutation both as a fetus and after birth.
Medical ethicists, alarmed at the prospect of "designer" babies, have consistently voiced concerns about PGD even though it appears so far to have been used only to avoid disease-carrying embryos.
"I think primarily this is going to be used for good," says Dr. Dena Towner, director of the prenatal diagnosis center at the University of California at Davis in Sacramento. "But you have to start wondering, are there going to be people with poor ethics" rummaging through embryos for personality traits like musical talent.
Yet, the procedure does raise questions about when it's appropriate to use PGD to avoid illness. After all, heart disease and many other ailments of late adulthood may turn out to have powerful genetic components that might be corrected at the embryo stage -- many decades before they would ever pose serious problems.
Also concerning in the Alzheimer's gene case, says Towner, co-author of an accompanying editorial, is that the child will almost certainly lose her mother to the disease by the time she's a teen-ager. Towner's own center doesn't offer PGD, but she said she would want to be sure the parents were appropriately informed and counseled about this future before they went ahead with the procedure.
Both Towner and Verlinsky agree questions of family structure should ultimately be left to parents.
"I think it's up to patients, the couples. They have to decide how they have to care about the future situation when only one parent's available" to raise the child, Verlinsky says. "There are plenty of examples when a family is raised by one parent."
The procedure runs about $2,500, far less than the cost of caring for a baby with a serious genetic disorder, Verlinsky adds.
Alzheimer's experts say the procedure would benefit only a sliver of patients.
"This is a such a tiny portion of the people that may get Alzheimer's that it's not a public health issue," says William Thies, vice president of medical and scientific affairs at the Alzheimer's Association.
What To Do
For more on Alzheimer's disease, try the Alzheimer's Association.
To learn more about PGD, check out Oregon Health Sciences University or the Genetics & IVF Institute.
