What are genetic diseases. Human hereditary diseases

As you know, all the appearance and other features of the baby depend on the set of genes that he received from both parents. For most of us, the question of heredity is only interesting for determining the color of the eyes and hair of the future baby, but the importance of genetics does not end there. Recently, even at the stage of planning a child, future parents are strongly encouraged to seek help from a geneticist, who will determine the probability of birth. healthy baby this particular pair. Such a specialist will help to calculate the possible risk of developing various genetic diseases that are inherited.

What is genetic inheritance?

The nucleus of every cell of our body has twenty-three pairs of chromosomes, which contain all hereditary information. Half of them we get from the mother's body together with the egg, and half from the father's - along with the sperm. The fusion of these germ cells leads to the birth of a new life. In the event that some gene of the parents is pathogenic, it can be passed on to the baby. If the bearer of such a code is only the father or only the mother, then the probability of transmission is significantly reduced.

In general, the chances of a child developing a genetic disease is only three to five percent. However, parents need not to rely on chance, but to take the planning of the baby seriously.
Let's try to figure out what kind of hereditary human genetic diseases that are inherited.

Down's disease

Down's disease is considered to be the most common genetic disease, as statistics show that one in seven hundred newborns suffers from it. Such a diagnosis is usually made by a neonatologist at the maternity hospital in the first five to seven days of life. To confirm this status of the baby, a study of the karyotype (set of chromosomes) in the baby is carried out. With Down syndrome, a child has one more chromosome - forty-seven pieces. This disease develops equally often in boys and girls.

Shershevsky-Turner disease

This disease develops only in girls. Its first signs become noticeable only at the age of ten or twelve and are expressed in short stature and low-set hair on the back of the head. Doctors are usually consulted because of the absence of menstruation. Over time, the disease leads to some mental problems. With Shershevsky-Turner disease, the girl lacks one X chromosome in the karyotype.

Klinefelter's disease

This ailment is diagnosed exclusively in males. Most often it is found in the age range from sixteen to eighteen years. Patients are tall - more than one hundred and ninety centimeters, often have some lag mental development and especially long handsdisproportionate to the body, which cover chest... The study of the karyotype shows one more X chromosome, in some cases it can be detected by the presence of other extra chromosomes - Y, XX, XY, etc. The main symptom of Klinefelter's disease is infertility.

Phenylkutonuria

This ailment is considered to be one of the most common genetic diseases. With this pathology, the body is unable to assimilate the amino acid phenylalanine, which leads to its accumulation in the body. Toxic concentrations of this substance adversely affect the activity of the brain, various organs and systems. The patient has a significant lag in mental and physical development, seizures, dyspeptic problems, and dermatitis appear. To correct phenylketonuria, a special diet is used, babies are given special amino acid mixtures that do not contain phenylalanine.

Cystic fibrosis

This disease is also considered to be relatively common. It is manifested by the defeat of all organs that produce mucus - the bronchopulmonary system suffers, digestive tract, liver, sweat, salivary and sex glands. Patients have manifestations chronic inflammation lungs, as well as bronchi, which are combined with dyspeptic problems - diarrhea, which are replaced by constipation, nausea, etc. Therapy involves the intake of enzyme preparations, as well as anti-inflammatory drugs.

Hemophilia

The disease is diagnosed exclusively in boys, although women carry the affected gene. Hemophilia is characterized by problems with blood clotting, which is fraught with a variety of complications and disorders. With this diagnosis, even a small cut is accompanied by prolonged bleeding, and a bruise leads to the formation of a huge subcutaneous hematoma. This kind of injury can be fatal. Hemophilia is treated by injecting the patient with the coagulation factor that is missing. Therapy should be continued throughout life.

We have considered only a few of the most famous and common genetic diseases that are inherited. In fact, their list is much more. Therefore, all couples who are planning to have children should consult with a qualified geneticist who can provide possible risks for their common child.

Each of us, thinking about a child, dreams of having only a healthy and ultimately happy son or daughter. Sometimes our dreams fail, and a child is born seriously ill, but this does not mean at all that this own, native, blood (scientifically: biological) child in the vast majority of cases will be less loved and less native.

Of course, at the birth of a sick child, there are immeasurably more worries, material costs, and physical and moral stress than at the birth of a healthy one. Some condemn the mother and / or father for refusing to raise a sick child. But, as the Gospel tells us: "Do not judge and you will not be judged." They refuse a child for a variety of reasons, both on the part of the mother and / or father (social, material, age, etc.), and the child (the severity of the disease, the possibility and prospects of treatment, etc.). The so-called abandoned children can be both sick and practically healthy people, regardless of age: as newborns and children infancyand older ones.

For various reasons, the spouses decide to take a child from orphanage or directly from the maternity hospital. Less often this, from our point of view, a humane civil act, is done by single women. It happens that children with disabilities leave the orphanage and their named parents deliberately take a child with Down's disease or with a child into the family cerebral palsy and other diseases.

The task of this work is to highlight the clinical and genetic characteristics of the most common hereditary diseases that appear in a child immediately after birth and then on the basis of clinical picture the disease can be diagnosed, or during the subsequent years of the child's life, when the pathology is diagnosed depending on the time of the appearance of the first symptoms specific to this disease. Some diseases can be detected in a child even before the appearance clinical symptoms using a number of laboratory biochemical, cytogenetic and molecular genetic studies.

The probability of having a child with a congenital or hereditary pathology, the so-called population or general statistical risk equal to 3-5%, haunts every pregnant woman. In some cases, it is possible to predict the birth of a child with one or another disease and diagnose the pathology already in the period of intrauterine development of the child. Some congenital defects and diseases are established in the fetus using laboratory biochemical, cytogenetic and molecular genetic techniques, more precisely, a set of methods for prenatal (prenatal) diagnostics.

We are convinced that all children proposed for adoption / adoption should be examined in detail by all medical specialists in order to exclude the corresponding profile pathology, including examined and examined by a geneticist. In this case, all known data about the child and his parents must be taken into account.

In the nucleus of every cell human body there are 46 chromosomes, i.e. 23 pairs, which contain all hereditary information. A person receives 23 chromosomes from a mother with an egg and 23 from a father with a sperm. When these two germ cells merge, we get the result that we see in the mirror and around us. A cytogenetic specialist is engaged in the study of chromosomes. For this purpose, blood cells called lymphocytes are used, which are specially processed. A set of chromosomes, distributed by a specialist in pairs and by serial number - the first pair, etc., is called a karyotype. We repeat, the nucleus of each cell contains 46 chromosomes or 23 pairs. The last pair of chromosomes is responsible for a person's gender. In girls, these are XX chromosomes, one of them is received from the mother, the other from the father. Boys have XY sex chromosomes. The first was received from the mother and the second from the father. Half of the sperm contains the X chromosome and the other half of the Y chromosome.

There is a group of diseases caused by a change in the set of chromosomes. The most common of these are down's disease (one per 700 newborns). The diagnosis of this disease in a child should be made by a neonatologist in the first 5-7 days of a newborn's stay in a maternity hospital and confirmed by examining the child's karyotype. In Down's disease, the karyotype is 47 chromosomes, the third chromosome is found in the 21st pair. Girls and boys suffer from this chromosomal pathology in the same way.

Only girls can have shereshevsky-Turner disease... The first signs of pathology are most often noticeable at the age of 10-12, when the girl has a small stature, low-set hair on the back of the head, at 13-14 years old there is no hint of menstruation. There is a slight lag in mental development. The leading symptom in adult patients with Shereshevsky-Turner disease is infertility. The karyotype of such a patient is 45 chromosomes. One X chromosome is missing. The incidence of the disease is 1 in 3,000 girls and among girls with a height of 130-145 cm - 73 per 1000.

Only males have kleinfelter's disease, which is diagnosed most often at the age of 16-18. The patient has a high growth (190 cm and above), often a slight lag in mental development, disproportionate to the growth of long arms, covering the chest with its girth. When studying the karyotype, 47 chromosomes are observed - 47, XXY. In adult patients with Kleinfelter's disease, infertility is the leading symptom. The prevalence of the disease is 1: 18,000 healthy men, 1: 95 boys with mental retardation and one among 9 men who are infertile.

Above, we have described the most common chromosomal diseases. More than 5,000 diseases of a hereditary nature are referred to as monogenic, in which there is a change, mutation, in any of the 30,000 genes found in the nucleus of a human cell. The work of certain genes contributes to the synthesis (formation) of the protein or proteins corresponding to this gene, which are responsible for the functioning of cells, organs and systems of the body. A disruption (mutation) of a gene leads to a violation of protein synthesis and further disruption of the physiological function of cells, organs and systems of the body, in which this protein is involved. Let's take a look at the most common of these diseases.

All children under the age of 2-3 months must certainly carry out a special biochemical study of urine to exclude them phenylketonuria or pyruvic oligophrenia... With this hereditary disease, the patient's parents - healthy people, but each of them carries exactly the same pathological gene (the so-called recessive gene) and with a risk of 25% they may have a sick child. More often, such cases occur in related marriages. Phenylketonuria is one of the most common hereditary diseases. The frequency of this pathology is 1: 10,000 newborns. The essence of phenylketonuria is that the amino acid phenylalanine is not absorbed by the body and its toxic concentrations adversely affect the functional activity of the brain and a number of organs and systems. Lagging mental and motor development, epileptiform-like seizures, dyspeptic manifestations (disorders of the gastrointestinal tract) and dermatitis (skin lesions) are the main clinical manifestations of this disease. Treatment consists mainly of a special diet and the use of amino acid mixtures devoid of the amino acid phenylalanine.

Children under 1-1.5 years old are recommended to carry out diagnostics to identify a serious hereditary disease - cystic fibrosis... With this pathology, damage to the respiratory system and the gastrointestinal tract is observed. The patient has symptoms of chronic inflammation of the lungs and bronchi in combination with dyspeptic manifestations (diarrhea followed by constipation, nausea, etc.). The incidence of this disease is 1: 2500. Treatment consists in the use of enzymatic drugs that support the functional activity of the pancreas, stomach and intestines, as well as the appointment of anti-inflammatory drugs.

More often, only after a year of life, clinical manifestations of a widespread and widespread known disease — hemophilia... Mostly boys suffer from this pathology. The mothers of these sick children are carriers of the mutation. Alas, sometimes, about the mother and her relatives in medical card child, nothing is written. The blood clotting disorder observed in hemophilia often leads to severe joint damage (hemorrhagic arthritis) and other damage to the body, with any cuts there is prolonged bleeding, which can be fatal for a person.

At 4-5 years of age and only in boys, clinical signs duchenne muscular dystrophy... As with hemophilia, the mother is a carrier of the mutation, i.e. "Conductor" or transmitter. Skeletal striated muscles, simpler, the muscles of the lower legs first, and over the years of all other parts of the body, are replaced by connective tissueunable to contract. The patient is waiting for complete immobility and death, more often in the second decade of life. So far, no effective therapy has been developed for Duchenne muscular dystrophy, although in many laboratories around the world, including ours, research is being carried out on the application of genetic engineering methods for this pathology. In the experiment, impressive results have already been obtained, which allow us to look with optimism to the future of such patients.

We have indicated the most common hereditary diseases that are detected using molecular diagnostic techniques even before the onset of clinical symptoms. We believe that the study of the karyotype, as well as the examination of the child to exclude common mutations, should be carried out by the institutions where the child is. In the medical data about the child, along with his blood group and Rh belonging, the data of the karyotype and molecular genetic studies, characterizing the state of the child's health at the present time and the likelihood of manifestation of the most frequent hereditary diseases in the future, must be indicated.

The proposed examinations will undoubtedly contribute to solving many global problems, both for the child and for people who want to take this child into their family.

V.G. Vakharlovsky - medical geneticist, pediatric neuropathologist the highest category, Candidate of Medical Sciences. Doctor of the genetic laboratory for prenatal diagnostics of hereditary and congenital diseases BEFORE. Otta - for more than 30 years he has been engaged in medical and genetic counseling on the prognosis of the health of children, the study, diagnosis and treatment of children suffering from hereditary and congenital diseases nervous system... Author of over 150 publications.

Laboratory for Prenatal Diagnostics of Hereditary and Congenital Diseases (Head of the Corresponding Member of the Russian Academy of Medical Sciences, Professor V.S.Baranov), Institute of Obstetrics and Gynecology named after BEFORE. Otta RAMS, St. Petersburg

This problem is long-standing and very serious, although no more than five percent of newborns suffer from hereditary diseases.

Hereditary diseases are the result of a defect in the genetic apparatus of cells, passed from parents to children and are already present during the intrauterine development of the fetus. Hereditary form may have diseases such as cancer, diabetes, heart defects, and many other diseases. Congenital diseasesmay result from abnormal development genes or chromosomes. Sometimes only a few abnormal cells will appear enough for a person to develop a malignant disease later.

Hereditary and congenital diseases in children

Concerning medical term "Genetic diseases" then it is applicable to those cases. When the moment of damage to the cells of the body occurs already at the stage of fertilization. Such diseases arise, among other things, due to a violation of the number and structure of chromosomes. Such a destructive phenomenon occurs as a result of improper maturation of the egg and sperm. These diseases are sometimes called chromosomal. These include such serious ailments as Down syndrome, Kleinfelter, Edwards and others. Modern medicine almost 4 thousand known various diseasesarising from genetic abnormalities. An interesting fact is that 5 percent of people have at least one defective gene in their bodies, but at the same time they are completely healthy people.

Terminology in the article

A gene is the initial unit of heredity, which is a part of a DNA molecule that influences the formation of protein in the body, and therefore signs of the state of the body. Genes are represented in binary form, that is, one half is passed on from the mother, and the other from the father.

Deoxyribonucleic acid (DNA) is a substance found in every cell. It carries in itself all the information about the state and development of a living organism, be it a person, an animal or even an insect.

Genotype is a set of genes acquired from parents.

Phenotype - set characteristic features the state of the organism during its development.

Mutations are persistent and irreversible changes in the genetic information about an organism.

Monogenic diseases are quite common, in which only one gene is damaged, which is responsible for a specific function of the body. Due to the fact that there are many such diseases, a certain classification of them has been adopted in medicine, which looks like this.

Autosomal dominant diseases.

This group includes diseases that occur when there is only one copy of the defective gene. That is, the patient has only one of the parents. Thus, it becomes clear that the offspring of such a sick person has a 50% chance of inheriting the disease. This group of diseases includes such diseases as Marfan's syndrome, Huntington's disease and others.

Autosomal recessive diseases.

This group includes diseases that arise due to the presence of two defective copies of a gene. At the same time, having given birth to a sick child can be absolutely healthy, but at the same time be carriers of one copy of a defective, mutated gene. In such a situation, the threat of having a sick child is 25%. This group of diseases includes such diseases as cystic fibrosis, sickle cell anemia and other ailments. Such carriers usually appear in closed societies, as well as in the case of related marriages.

X-linked dominant diseases.

This group includes diseases that arise due to the presence of defective genes in the female sex X chromosome. Boys are more likely to suffer from these diseases than girls. Although a boy born of a sick father may not transmit the disease to his offspring. As for girls, then they all will necessarily have a defective gene. If the mother is sick, then the probability of inheriting her disease for boys and girls is the same and it is 50%.

X-linked recessive diseases.

This group includes those diseases that are caused by mutations in genes located on the X chromosome. In this case, boys are more at risk of inheriting the disease than girls. Likewise, a sick boy may not later pass on the disease to his children. Girls will have one copy of the defective gene anyway. If the mother is the carrier of the defective gene, then she can, with a 50% probability, give birth to a sick son or a daughter who will become a carrier of such a gene. This group of diseases includes such diseases as hemophilia A, Duchenne muscular dystrophy and others.

Multifactorial or polygenic genetic diseases.

This includes those diseases that arise as a result of a malfunction of several genes at once, and under the influence of external conditions. The heredity of these diseases is manifested only relatively, although the diseases are often family characteristics. These are diabetes, heart disease and some others.

Chromosomal diseases.

This includes those diseases that occur due to a violation of the number and structure of chromosomes. With these signs, women often experience miscarriages and miscarriages. Children of such women are born with both mental and physical abnormalities. Such cases, alas, occur quite often, namely in one of the twelve fertilizations. The results of such sad statistics are not visible due to the termination of pregnancy at a certain stage of fetal development. As for the children born, statistics say that one out of one hundred and fifty newborns are born with this disease. Already in the first trimester of pregnancy, half of women with fetal chromosomal diseases experience miscarriages. This indicates that the treatment is ineffective.

Before talking about the prevention of hereditary and congenital diseases, it is worth spending some time on issues related to polygenic or multifactorial diseases. These diseases occur in adults and often become reasons for concern about the feasibility of having offspring and the likelihood of the transfer of diseases from parents to children. Such diseases are the most common in this group.

Diabetes mellitus of the first and second types .

This disease is partially hereditary. Type 1 diabetes can also develop due to a viral infection or due to prolonged nervous disorders. Examples are noted when diabetes-1 resulted from allergic reaction to an aggressive environment and even to medical drugs... Some people with diabetes carry a gene that is responsible for the likelihood of developing the disease in childhood or adolescence. As for type 2 diabetes, there is clearly a hereditary nature of its occurrence. The highest probability of developing type 2 diabetes is already in the first generation of the carrier's offspring. That is, his own children. This probability is 25%. However, if the husband and wife are also relatives, then their children will inherit parental diabetes without fail. The same fate awaits identical twins, even if their diabetic parents are not related.

Arterial hypertension.

This disease is the most typical of the category of complex polygenic diseases. In 30% of cases of its occurrence, there is a genetic component. With the development of arterial hypertension, at least fifty genes take part in the disease, and over time their number grows. The abnormal effect of genes on the body occurs under the influence of environmental conditions and the body's behavioral reactions to them. In other words, despite the hereditary predisposition of the body to the disease of arterial hypertension, healthy image life in treatment plays a huge role.

Violation of fat metabolism.

This disease is the result of the influence of genetic factors in conjunction with a person's lifestyle. Many genes are responsible for the metabolism in the body, for the formation of fat mass and for the strength of a person's appetite. Failure of only one of them can lead to the appearance of various diseases. Outwardly, a violation of fat metabolism manifests itself in the form of obesity of the patient's body. Among obese people, fat metabolism is impaired only in 5% of them. This phenomenon can be massively observed in some ethnic groups, which confirms the genetic origin of this disease.

Malignant neoplasms.

Cancer tumors do not appear as a result of heredity, but haphazardly and can even be said by chance. Nevertheless, in medicine, isolated cases have been recorded when cancerous tumors arose precisely as a result of heredity. It is mainly cancer of the breast, ovary, rectum and blood. The reason for this is a congenital mutation of the VYASA1 gene.

Impaired mental development.

The hereditary factor is most often the cause of mental development disorders. Parents of a mentally retarded child often carry a variety of mutant genes. Often they have disrupted the interaction of individual genes or there are violations of the number and structure of chromosomes. Down syndrome, fragile X syndrome and phenylketonuria are characteristic here.

Autism.

This disease is associated with impaired functionality of the brain. It is characterized by poorly developed analytical thinking, stereotypical behavior of the patient and his inability to adapt to society. The disease is detected by the age of three years of a child's life. Doctors associate the development of this disease with improper synthesis of proteins in the brain due to the presence of gene mutations in the body.

Prevention of congenital and hereditary diseases

It is customary to share preventive measures against such diseases into two categories. These are primary and secondary measures.

The first category includes such measures as identifying the risk of a disease at the stage of planning conception. It also includes measures for the diagnosis of fetal development by the method of systematic examinations of a pregnant woman.

When planning pregnancy, in order to prevent hereditary diseases, it is worth contacting the regional clinic, where the archival data on the health of the spouses' ancestors are stored in the "Family and Marriage" database. As for the medical and genetic consultation, it is necessary if the spouses have chromosomal changes, hereditary diseases and, of course, in the case of an abnormal development of the fetus or an already born child. In addition, such advice must be obtained if the husband and wife are in family ties. Consultation is extremely necessary for those couples who have had miscarriages or children were born dead before. It will be useful for all women who will give birth for the first time at the age of 35 or more.

At this stage, a study of the pedigree of both spouses is carried out, based on the medical data available in the archive about the health of the previous generations of the husband and wife. In this case, it is possible to identify with almost absolute accuracy whether there is a probability of a hereditary disease in the unborn child, or there is none. Before going to a consultation, spouses need to ask their parents and relatives in as much detail as possible about those diseases that took place in previous generations of the family. If there are hereditary diseases in the history of the genus, then it is necessary to tell the doctor about this. This will make it easier for him to determine the necessary preventive measures.

Sometimes on stage primary prevention it is necessary to analyze the state of the chromosome set. This analysis is done for both parents, since the child will inherit half of the chromosome from mom and dad. Unfortunately, perfectly healthy people can be carriers of balanced chromosomal rearrangements without even suspecting the presence of such a deviation in their bodies. If a child inherits a chromosomal rearrangement from one of the parents, then the likelihood of serious illnesses will be quite high.

Practice shows that in such a family the risk of having a child with a balanced chromosomal rearrangement is about 30%. If spouses have rearrangements in the chromosome set, then during pregnancy, using PD, you can prevent the birth of an unhealthy child.

As part of the primary prevention of occurrence congenital anomalies the child's nervous system, such a method as the appointment of folic acid, which is a solution of vitamins in water, is widely used. Before pregnancy, a sufficient amount of folic acid enters the woman's body in the process of adequate nutrition. If she adheres to any diet, then of course, the intake of acid may not be in the amount required by the body. In pregnant women, the body's need for folic acid increases by one and a half times. It is not possible to provide such an increase only with the help of the diet.

By the way, this is the only vitamin that during pregnancy should enter the body in a larger amount than before pregnancy. It is possible to satisfy the complete need of a pregnant woman's body for folic acid only through its additional use. Folic acid has unique properties. So, additional intake of this vitamin two months before conception and during the first two months of pregnancy reduces the likelihood of abnormal abnormalities in the central nervous system of the child three times! Usually, the doctor prescribes the intake of standard pills, four pieces per day. If the first child had some deviation in the development of the central nervous system, and the woman decided to give birth again, then she needs to increase the amount of folic acid taken by two, or even two and a half times.

Secondary prevention of congenital and hereditary diseases

This includes preventive measures that are already applied when it is known for sure that the fetus in the body of a pregnant woman develops with pathological deviations from the norm. If such a sad circumstance is found, the doctor must inform both parents about this and recommend certain procedures to correct the development of the fetus. The doctor must explain exactly how the child will be born and what awaits him as he grows up. After that, the parents decide for themselves whether it is worth giving birth to a child or whether it is better and more humane to terminate the pregnancy on time.

Two methods are used to diagnose the condition of the fetus. These are non-invasive measures that do not require physical intervention and invasive measures in which a sample of fetal tissue is taken. The essence of non-invasive measures is to test the mother's blood and conduct ultrasound diagnostics her body and the body of the fetus. Recently, doctors have mastered the technology of taking a blood test from the fetus. The sample is taken from the maternal placenta, into which the fetal blood enters. This process is quite complicated, but also quite effective.

The mother's blood test is usually done at the end of the first - beginning of the second trimester of pregnancy. If two or three substances in the blood are present in abnormal amounts, then this may be a sign of a hereditary disease. In addition, at the end of the first trimester of pregnancy, human chorionic gonadotropin is determined from the mother. This is a pregnancy hormone that is produced by the placenta in a woman's body and in turn produces serum protein A. In the second trimester of pregnancy, an analysis is made for the content of hCG, alpha-fetoprotein, unbound (free) estriol.

The complex of such measures in the world medicine is called "triple panel", and in general the technique is called "biochemical screening".

During the first trimester of pregnancy, the concentration of hCG in the blood serum doubles daily. After the complete formation of the placenta, this indicator stabilizes and remains unchanged until delivery. HCG supports the production of hormones in the ovaries necessary for the normal course of pregnancy. In the mother's blood, not the entire hormone molecule is determined, but only the p-subunit. If the fetus has chromosomal diseases, in particular Down's syndrome, the hormone content in the mother's blood serum is significantly overestimated.

Whey protein A is produced in the mother's body in the tissue of the placenta. If the fetus has a chromosomal disorder, then the amount of protein will be underestimated. It should be noted that such changes can be recorded only from the tenth to the fourteenth week of pregnancy. In the subsequent time, the level of protein in the mother's blood serum returns to normal.

Alpha-fetoprotein (AFP) is already produced in the tissues of the embryo and continues in the tissues of the fetus. The function of this component is not fully understood. It is determined in a woman's blood serum or amniotic fluid as a marker congenital defects central nervous system, kidney or anterior abdominal wall... It is known that for oncological diseases this protein is found in blood serum in both adults and children. As the fetus develops, this protein is transferred from the fetal kidneys to the mother's blood through the placenta. The nature of the change in its amount in the mother's serum depends both on the presence of a chromosomal disease in the fetus, and on some features of the course of the pregnancy itself. Thus, the analysis of AFP without assessing the functionality of the placenta from the point of view of the diagnostic accuracy is not decisive. Nevertheless, AFP as a biochemical marker of congenital diseases has been well studied.

AFP is most accurately determined during the second trimester of pregnancy, namely between the sixteenth and eighteenth weeks. Until that time, from the point of view of diagnostic accuracy, it makes no sense to determine this protein. If the fetus has a congenital malformation of the central nervous system or the anterior abdominal wall, then the AFP level in the mother's blood serum will be significantly higher than normal. If the fetus suffers from Down syndrome or Edwards, then on the contrary, this indicator will be below normal.

The hormone estriol is produced by both the maternal placenta and the fetus itself. This hormone ensures the normal course of pregnancy. The level of this hormone in the mother's blood serum also increases progressively under normal conditions. If the fetus has a chromosomal disease, then the level of unbound estriol in the mother's body is much lower than the norm for a normal pregnancy. The study of the level of the hormone estriol makes it possible to determine with sufficient accuracy the likelihood of having a child with a hereditary disease. However, only experienced specialists can interpret the results of the analysis, because this process is quite complicated.

Biochemical screening is a very important procedure. In addition, this method has several advantages. It does not require surgical intervention in the mother's body and is not a technologically complex process. At the same time, the effectiveness this study very high. However, this method is not without its drawbacks. In particular, it allows you to determine only the degree of likelihood of a congenital disease, and not the fact of its presence. In order to identify this presence with accuracy, additional diagnostic testing is required. The saddest thing is that the results of biochemical screening can be completely normal, but the fetus has a chromosomal disease. This technique requires the most accurate determination of the date of fertilization and is not suitable for the study of multiple pregnancies.

Ultrasound procedure

Devices for ultrasound diagnostics are constantly being improved. Modern models allow you to see the fetus even in a volumetric image format. These devices have been used in medicine for a long time, and during this time it has been fully proven that they do not have any negative impact on either the health of the fetus or the health of the mother. According to medical regulations in force in Russian Federation, ultrasound examination of pregnant women is performed three times. The first time it is done in the period of 10-14 weeks of pregnancy, the second 20-24 and the third 32-34 weeks. The first study determines the duration of pregnancy, the nature of its course, the number of fetuses, and the state of the mother's placenta is described in detail.

With the help of ultrasound, the doctor finds out the thickness of the collar space along the back of the fetus's neck. If the thickness of this part of the fetus's body is increased by three or more millimeters, then in this case there is a possibility that the child will develop chromosomal diseases, including Down's syndrome. In this case, the woman is assigned an additional examination. At this stage of pregnancy, the doctor checks the development of the fetal nasal bone. If the fetus has a chromosomal disease, the nasal bone will be underdeveloped. With such a detection, an additional examination of the mother and fetus is also required.

During the second study, at 10-24 weeks of gestation, the fetus is examined in detail for the presence of developmental defects and signs of chromosomal diseases. The condition of the placenta, cervix and amniotic fluid is also assessed.

Almost half of fetal malformations can be detected during ultrasound examination in the period 20-24 weeks of pregnancy. In this case, the remaining half, in fact, may not be detected at all by any of the currently known diagnostics. Thus, it is impossible to say that diagnostics can one hundred percent determine the presence of a congenital disease in a fetus. Nevertheless, it is necessary to do it, at least for the sake of that half of the cases that are determined with accuracy.

The impatience of parents to find out who will be born to them, a girl or a boy, is understandable. It should be said that conducting a study just for the sake of curiosity is not recommended, especially since in five percent of cases it is not possible to accurately determine the gender of the child.

Very often, the doctor prescribes repeated examination for pregnant women, and this scares many. However, you should not panic because only 15% of repeated examinations are associated with signs of abnormal fetal development. Of course, in this case, the doctor must tell both parents about it. In other cases, the re-examination is associated either with a safety net or with the peculiarity of the location of the fetus.

At the stage of pregnancy at 32 -34 weeks, the study determines the rate of fetal development and reveals signs of defects characteristic of their late manifestation. If any pathology is detected, a pregnant woman is asked to analyze a tissue sample of the fetus or placenta.

Chorionic biopsy (placenta) can be done at 8 to 12 weeks of gestation. This procedure is performed on an outpatient basis. For analysis, no more than five to ten milligrams of tissue is taken. Such an insignificant amount is quite enough for analyzing the number and structure of chromosomes. This method makes it possible to accurately determine the presence or absence of a chromosomal disease.

Amniocentesis is a technique for collecting amniotic fluid for analysis. They begin to be produced in the body of a pregnant woman soon after conception. Fetal cells are present in the amniotic fluid. When analyzed, these cells can be isolated and examined. Typically, this test is done between 16 and 20 weeks of gestation. In this case, no more than 20 milliliters of water is taken, which is absolutely safe for a woman and a fetus. Another method of “early amniocentesis” is also used, which can be performed at the end of the first trimester of pregnancy. Recently, it has been rarely used. This is due to the fact that in last years cases of fetal limb defects have become more frequent.

Cordocentesis is also called intrauterine puncture of the umbilical cord. This technique is used to obtain a fetal blood sample for further laboratory testing. This analysis is usually done between 20 and 24 weeks of pregnancy. The amount of blood required for a complete analysis is about three to five grams.

It should be said that all of the above methods are, to a certain extent, fraught with unpleasant consequences. In particular, statistics show that after carrying out such studies, one to two percent of women have a pregnancy terminated. Thus, these tests are best done when the likelihood of a fetus developing congenital diseases is too high. At the same time, the importance of these analyzes cannot be denied, since they allow to identify even one altered gene in the fetus. Nevertheless, invasive methods are gradually becoming a thing of the past, and new technologies are replacing them. They allow the cells of the fetus to be removed from the mother's blood.

Thanks to the development in the treatment of infertility such a method as in vitro fertilization, it became possible to carry out preimplantation diagnostics. Its essence is as follows. The oocyte is artificially fertilized in laboratory conditions and placed in an incubator for a certain time. Here cell division occurs, that is, in fact, the formation of the embryo begins. It is at this time that you can take one cell for research and conduct a complete DNA analysis. Thus, you can find out exactly how the fetus will develop later, including in terms of the likelihood of hereditary diseases.

At the end of the article, it should be emphasized that the main goal of all these studies is not only to identify the presence or absence of a hereditary disease in the fetus, but also to promptly warn the parents and sometimes relatives of the unborn baby about this. It often happens that there is no hope for the correction of any pathology identified in the fetus, just as there is no hope that the born child will be able to develop normally. In such a tragic situation, doctors recommend that parents artificially terminate the pregnancy, although the final decision on this matter is made by the parents. However, at the same time, they need to take into account that the tragedy of termination of pregnancy is not commensurate with the tragedy that will happen when a disabled child is born.

Bacteria, viruses and infections are not always the cause of the disease. Some diseases are programmed in us even before birth. 70% of people have some deviations from the norm in their genotype. In other words, faulty genes. But out of 70%, not all have genetic diseases. What are the most common genetic diseases?

What is a genetic disease

A genetic disease is a disease caused by damage to the software apparatus of cells. Since they are inherited, they are also called hereditary diseases. These diseases are transmitted only from parents to children, there are no other ways of infection.

Down Syndrome With Down syndrome, 1 child is born in 1100. People with this chromosomal abnormality are significantly behind in physical and mental development. Spina bifida With such a violation, 1 child is born out of 500-2000 children. Although in early age you can correct the anomaly with surgery, the risk of complications is too great. Cystic fibrosis The disease is the cause of disturbances in the functioning of the excretory glands, digestive and respiratory systems. In European countries, the frequency of this genetic mutation is 1: 2000 - 1: 2500. Neurofibromatosis This common genetic disorder is characterized by the appearance of many small tumors in the patient. It occurs in one out of 3500 newborns. Color blindness Violations in the gene code lead to color recognition problems. There are many types of color blindness, depending on what color the patient does not perceive with his eyes. Various degrees of color blindness affects 2-8% of men, and only 0.4% of women. Klinefelter's syndrome One in 500 newborn boys has this anomaly. It manifests itself in high growth, large body weight and a large number of female hormones. All patients suffer from infertility. Prader-Willi syndrome It occurs once every 12-15 thousand newborns, patients are short and obese. You can help the sick with medication. Turner syndrome This gene disorder affects 1 in 2,500 newborn girls. All patients have short stature, increased body weight and short fingers. Angelman syndrome Symptoms of the disease: developmental delay, chaotic movements and emotional reactions, epilepsy is observed in 80% of patients. With this disease, 1 child is born in 10 thousand. Hemophilia This incurable disease affects men. Hemophilia is a blood clotting disorder. Patients suffer from internal hemorrhages. The incidence of the disease is 1: 10000. Phenylketonuria This disease causes disruption of amino acid metabolism and damage to the central nervous system. The incidence of the disease in European countries is 1: 10000.

Hereditary diseases are one of the worst diseases. There is simply no cure for many of them. Very often, parents are only carriers of the defective gene, and the disease is recouped in the child. Many male genetic diseases are maternal and vice versa. If Down's syndrome or spina bifida is diagnosed in a child while still in the womb, then she is offered an abortion. The life of most people with hereditary diseases is very difficult. But diseases such as color blindness, hemophilia, Turner syndrome and many others do not pose a great danger. You can live normally with them or cope with problems with hormonal drugs.

List of Genetic Diseases * Main Articles: Hereditary Disorders, Hereditary Metabolic Diseases, Fermentopathy. * In most cases, a code is also provided to indicate the type of mutation and the associated chromosomes. also ... ... Wikipedia

Below is a list of symbolic ribbons (symbolic, or notification ribbon, from the English Awareness ribbon) a small piece of ribbon folded into a loop; is used to demonstrate the attitude of the tape carrier to a question or ... ... Wikipedia

This page is a glossary. See also: List of genetic malformations and diseases. Genetic terms in alphabetical order ... Wikipedia

A service list of articles created to coordinate work on the development of the topic. This warning did not install ... Wikipedia

A section of human genetics devoted to the study of the role of hereditary factors in human pathology at all major levels of life organization, from population to molecular genetic. The main section of M.G. constitutes clinical genetics, ... ... Medical encyclopedia

Hereditary diseases are diseases, the occurrence and development of which is associated with defects in the software apparatus of cells, which are inherited through gametes. The term is used in relation to polyetiological diseases, in contrast ... Wikipedia

Diseases, the occurrence and development of which is associated with defects in the software apparatus of cells, inherited through gametes. The term is used in relation to polyetiological diseases, in contrast to the narrower group Gene ... ... Wikipedia

Hereditary disease of a disease, the occurrence and development of which is associated with defects in the software apparatus of cells, inherited through gametes. The term is used in relation to polyetiological diseases, in contrast to ... ... Wikipedia

Hereditary metabolic disorders include large group hereditary diseases affecting metabolic disorders. Such disorders constitute a significant part of the group of metabolic disorders (metabolic diseases). ... ... Wikipedia

Books

• Childhood diseases, Belopolsky Yuri Arkadievich. The health of a child of any age is a special task for a doctor, because a growing body requires more attention and more vigilance in relation to diseases. Routine dispensaries, detection ...
• Introduction to molecular diagnostics and gene therapy of hereditary diseases, V. N. Gorbunova, V. S. Baranov. The book sets out modern views about the structure of the human genome, methods of its study, study of genes, mutations of which lead to severe hereditary pathology: considered ...