Are hereditary diseases threatening your future children?
Hereditary diseases: treat or prevent?
Vladimir Fradkin, Deutsche Welle
The new rapid test, currently undergoing clinical trials, is able to detect almost 600 genetic mutations in married couples, fraught with the development of severe ailments in their offspring. But it is not a panacea either...
People who do not have genetic defects at all simply do not exist in the world – which is quite understandable if we keep in mind the huge number of genes and the complexity of their structure. It would seem that we all have to suffer from a lot of hereditary diseases for this reason. However, the vast majority of the world's population does not have these ailments. This is explained by the fact that in the genome of each person, genes are represented by two copies, the so–called alleles – one from the father, the other from the mother - and defective copies are recessive, do not manifest themselves, because they are neutralized by healthy dominant copies. Only in a situation when both the father and the mother have a defect of the same gene, and the child inherits from each of the parents exactly the recessive allele of this gene, the disease will manifest itself. There are more than a thousand such systemic diseases with an autosomal recessive type of inheritance today. The most famous of them is cystic fibrosis, or cystic fibrosis, but the vast majority is so rare that non–specialists have not even heard of such names, as a rule.
Amaurotic idiocy is an incurable disease
A typical example of such an exotic disease is amaurotic juvenile idiocy, aka neural waxy lipofuscinosis, aka Stock-Spielmeier-Vogt disease, aka Batten-Mayo disease, aka Othman disease. Stephen F. Kingsmore, a prominent American pediatrician, specialist in hereditary diseases and director of the Center for Genomics and Bioinformatics at the Children's Hospital in Kansas City, tells about one of his patients - 10-year–old Christiane Benson: "She was diagnosed with the disease in March 2008, she had just turned 8 years old. She seemed to be a perfectly healthy child, when suddenly she began to have problems with her eyesight. Today she is almost completely blind. True, the girl continues to go to school, her parents insist on this, but they themselves told me that she is not able to remember anything of what they teach her there."
Stephen Kingsmore knows that the prognosis is disappointing: the physical and mental abilities of the unfortunate girl will continue to decrease, and she will hardly live to 18 years. The child's parents had no idea that they were suffering from the same genetic defect until it appeared in their daughter, because each of them had a healthy copy of this gene dominant, and it prevailed, and Christiana inherited a recessive defective allele from both her mother and father. Medicine cannot offer any treatment to such patients yet.
One fund – two goals"Christiana's father heads one of the biotech companies," says Stephen Kingsmore. "The tragedy of his daughter prompted him to take action.
He founded a charitable foundation and raised quite a lot of money, while pursuing two goals: firstly, to find at least some way to treat the specific disease that Christiana suffers from, and secondly, to overcome all diseases with an autosomal recessive type of inheritance in general."
This second goal prompted the father of a terminally ill girl to turn to Stephen Kingsmore. The head of the charitable foundation set a task for the scientists: to develop an express test that would allow married couples to learn in advance about dangerous mutations in their genome, fraught with the development of severe hereditary diseases in their offspring. In principle, separate tests for some of these diseases – for example, for cystic fibrosis – already exist, but they do not go to any comparison with what Stephen Kingsmore and his colleagues have now managed to develop: their test "combs" the genome for almost 600 hereditary diseases at once, and several are enough for this analysis drops of blood.
"We tested our test on 104 patients,– says Stephen Kingsmore. – It was known in advance about most of them that there were dangerous mutations in their genome, but it was important for us to make sure that our test really functions and reliably detects all mutations. So, the reliability of the test was 99.98 percent."
The test solves old problems and creates new onesThe next, much more extensive stage of testing is scheduled for the middle of this year.
The Berlin Charité University Clinic is likely to take part in it. Thus, the day is not far off when a unique rapid test will enter into everyday clinical practice. And this is a completely new situation – both for patients and for doctors, – says Peter Propping, professor of genetics at the University of Bonn: "If both parents are characterized by mixed heredity relative to the same mutation, then the probability that their child will be sick is 25 percent.
Based on this, they can do the following: either abandon the intention to have children altogether; or take a risk – in the hope that they will be lucky; or make a prenatal (prenatal) diagnosis for the detection of this disease in the fetus and, in case of an unfavorable result, terminate the pregnancy; or, finally, decide on artificial insemination with preimplantation diagnostics, which will allow us to weed out defective embryos and get healthy offspring."
In other words, the rapid test developed by Stephen Kingsmore puts married couples in front of a very difficult choice. And besides, this test, although it is able to identify almost 600 ailments, itself generates new problems. "Some of these hereditary diseases are quite treatable, and therefore, in general, should not be a cause for concern," explains Professor Propping. "One more aspect should not be forgotten: if such tests begin to be carried out on a massive scale, then the incentive to develop therapy for these diseases will disappear. Clinics and pharmaceutical concerns will refer to the fact that the new test allows you to simply avoid such diseases."
One way or another, each married couple will have to decide for themselves whether to conduct such a test or not. However, it is very important, Stephen Kingsmore believes, that at the same time they should definitely seek advice from a specialist.
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27.01.2011