Originally created 03/05/02

Another promising step along the genetics highway



Medicine has taken another promising step along the genetics highway, raising not only hopes, but the hair on some necks.

Medical geneticists have been able to assure a young mother that she won't pass along a rare form of Alzheimer's disease to her children.

That sounds like a pretty good thing. And as a matter of fact, it is.

But like every other technological breakthrough of our era, it is causing some people to wonder what else might end up broken. That's OK. It helps bioethicists and TV commentators make a living.

More important, it keeps our eyes on the road ahead, where inattention can lead to a nasty crash.

The procedure currently causing comment is described in the Feb. 27 issue of the Journal of the American Medical Association.

Tests showed that the patient, a married woman in her 30s, had inherited a gene mutation called V7171. It causes a rare, early-onset form of Alzheimer's by forming protein deposits that clog the brain. And the mutation is one, the article says, that can be passed on to her children.

The anonymous woman has a sister and brother in their 30s who already have developed the mind-wasting disease. She is a virtual certainty to suffer the same fate - an inheritance from her mother.

But two years ago her strong desire to have a child led her to seek a pre-implantation genetic diagnosis (PGD).

Yury Yerlinsky, a geneticist at the Reproductive Genetics Institute in Chicago, used her husband's sperm in the laboratory to fertilize ova surgically removed from her ovaries.

The process, used in tens of thousands of births each year to help couples overcome childlessness, is called in-vitro fertilization (IVF).

In this case, however, the microscopic embryos were examined for the mutation before being implanted in the woman's womb. Only embryos free of the mutation were implanted.

The result was a baby girl born a little more than a year ago, and free of the mutation.

According to Verlinsky, the woman has had the procedure repeated and is pregnant again.

What does all this mean in the big picture?

Well, IVF is not new. Neither is examination of an embryo for inherited diseases. Geneticists have used PGD for decades to prevent inheritance of diseases like Tay-Sachs, which is fatal to babies.

This is what's new: The little girl described in JAMA is the first child at risk for early-onset Alzheimer's to be born after intervention by PGD

Some questions this new step raises:

- If we can prevent the inheritance of Tay-Sachs and early-onset Alzheimer's, does it mean we're in the age of designer genes? Will parents soon be choosing their kids' eye and hair color, or ordering an extra helping of IQ?

Certainly not. Not for a long time, if ever. There is a big difference between confirming the absence of a mutation and fine-tuning something like intelligence.

- Does a couple's urge to have a child "of their own" justify the use of scarce medical resources ? If yes, for how many times? Once? Twice? Five times?

- Should finances determine which couples have access to such a procedure? Or, among couples with genetically detectable inherited conditions, are the less-well-off just out of luck?

The mother we're talking about had access to expensive, high-tech procedures, as well as a depth of knowledge about PGD.

When this is no longer experimental, and becomes available to the public, what will it cost? (News reports quoted a price of around $10,000 for this case, but IVF alone is likely to have a price closer to four times that much.)

- The mother in question will not likely be able to care for her child, or even recognize her, in another few years - after the cruel brain condition more fully develops in her. Is anybody thinking about the life the little girl faces - losing her mom, first to dementia and then to a premature death?

Regardless of what provisions will have been made for her continued care - and that of the baby on the way - it is likely to be a painful childhood.