V.G. Vakharlovsky - medical geneticist, pediatric neurologist highest category, candidate medical sciences. Doctor of the genetic laboratory for prenatal diagnosis of hereditary and congenital diseases of IAH named after. TO. Otta - for more than 30 years he has been engaged in medical and genetic counseling on the prognosis of the health status of children, the study, diagnosis and treatment of children suffering from hereditary and congenital diseases of the nervous system. Author of more than 150 publications.
Each of us, thinking about a child, dreams of having only a healthy and ultimately happy son or daughter. Sometimes our dreams are crushed, and a child is born seriously ill, but this does not mean at all that this dear, blood (scientifically: biological) child in the overwhelming majority of cases will be less loved and less dear. Of course, when a sick child is born, worries, material costs, and stress - physical and moral - arise immeasurably more than when a healthy one is born. Some people condemn a mother and/or father who abandons a sick child. But, as the Gospel tells us: “Judge not and you will not be judged.” They abandon the child for a variety of reasons, both on the part of the mother and/or father (social, material, age, etc.) and the child (severity of the disease, the possibility and prospects of treatment, etc.). So-called abandoned children can be both sick and practically healthy people, regardless of age: both newborns and children infancy, and older ones.
Due to various circumstances, the spouses decide to take a child into the family from orphanage or straight from the maternity hospital. Less often, this, from our point of view, humane, courageous civil act, is done by single women. It happens that orphanage disabled children are abandoned and their named parents consciously take into the family a child with an illness or with childhood cerebral palsy etc.
The purpose of this work is to highlight the clinical and genetic features of the most common hereditary diseases that appear in a child immediately after birth and then, based on the clinical picture of the disease, a diagnosis can be made, or during the subsequent years of the child’s life, when the pathology is diagnosed depending on time the appearance of the first symptoms specific to this disease. Some diseases can be detected in a child even before clinical symptoms using a number of laboratory biochemical, cytogenetic and molecular genetic studies.
The likelihood of having a child with a congenital or hereditary pathology, the so-called population or general statistical risk of 3-5%, haunts every pregnant woman. In some cases, it is possible to predict the birth of a child with a particular disease and diagnose the pathology already in the prenatal period. Some congenital defects and diseases are diagnosed in the fetus using laboratory-biochemical, cytogenetic and molecular genetic techniques, or more precisely, a set of prenatal (antenatal) diagnostic methods.
We are convinced that all children offered for adoption should be examined in detail by all medical specialists in order to exclude relevant specialized pathologies, including examination and examination 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 containing all hereditary information. A person receives 23 chromosomes from the mother with the egg and 23 from the father with the sperm. When these two sex cells merge, the result that we see in the mirror and around us is obtained. The study of chromosomes is carried out by a cytogeneticist. For this purpose, blood cells called lymphocytes are used, which are specially treated. A set of chromosomes, distributed by a specialist into 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 determines the sex of a person. 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 is received from the mother and the second from the father. Half of the sperm contain the X chromosome and the other half the Y chromosome.
There is a group of diseases that are caused by a change in the set of chromosomes. The most common of these is Down syndrome (one in 700 newborns). The diagnosis of this disease in a child must be made by a neonatologist in the first 5-7 days of the newborn’s stay in the maternity hospital and confirmed by examining the child’s karyotype. In Down syndrome, the karyotype is 47 chromosomes, the third chromosome is found on the 21st pair. Girls and boys suffer from this chromosomal pathology equally.
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 small stature, low-set hair on the back of her head, and at 13-14 years there is no hint of menstruation. There is a slight mental retardation. 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 in 1,000.
Only males experience Kleinfelter's disease, the diagnosis of which is most often made at 16-18 years of age. The patient has a high height (190 cm and above), often a slight mental retardation, long arms disproportionate to the height, covering the chest when circling it. When studying the karyotype, 47 chromosomes are observed - 47, XXY. In adult patients with Kleinfelter's disease, the leading symptom is infertility. The prevalence of the disease is 1: 18,000 healthy men, 1: 95 boys with a lag mental development and one among 9 men experiencing infertility.
Above we have described the most common chromosomal diseases. More than 5,000 diseases of a hereditary nature are classified as monogenic, in which there is a change, a 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 disruption of protein synthesis and further disruption physiological function cells, organs and body systems in which the protein is involved. Let's look at the most common of these diseases.
Not only can they be inherited external signs, but also diseases. Malfunctions in the genes of ancestors ultimately lead to consequences in the offspring. We will talk about the seven most common genetic diseases.
Hereditary properties are passed on to descendants from ancestors in the form of genes arranged in blocks called chromosomes. All cells of the body, with the exception of sex cells, have a double set of chromosomes, half of which comes from the mother, and the second part from the father. Diseases caused by certain malfunctions in genes are hereditary.
Myopia
Or myopia. A genetically determined disease, the essence of which is that the image is formed not on the retina, but in front of it. The most common cause of this phenomenon is considered to be increased length eyeball. As a rule, myopia develops during adolescence. At the same time, a person sees perfectly near, but poorly sees into the distance.
If both parents are nearsighted, then the risk of developing myopia in their children is over 50%. If both parents have normal vision, then the probability of developing myopia is no more than 10%.
Studying myopia, employees of the Australian National University in Canberra came to the conclusion that myopia is inherent in 30% of representatives Caucasian and affects up to 80% of natives of Asia, including residents of China, Japan, South Korea etc. Having collected data from more than 45 thousand people, scientists identified 24 genes associated with myopia, and also confirmed their connection with two previously established genes. All these genes are responsible for the development of the eye, its structure, and the transmission of signals in the eye tissue.
Down syndrome
The syndrome, named after the English physician John Down, who first described it in 1866, is a form of chromosomal mutation. Down syndrome affects all races.
The disease is a consequence of the fact that in cells there are not two, but three copies of the 21st chromosome. Geneticists call this trisomy. In most cases, the extra chromosome is passed on to the child from the mother. It is generally accepted that the risk of having a child with Down syndrome depends on the age of the mother. However, because young births in general are more common, 80% of all children with Down syndrome are born to women under the age of 30.
Unlike genetic disorders, chromosomal disorders are random failures. And there can be only one person in a family suffering from such a disease. But here, too, there are exceptions: in 3-5% of cases, rarer translocation forms of Down syndrome are observed, when the child has a more complex structure of the chromosome set. A similar variant of the disease can be repeated in several generations of the same family.
According to the Downside Up charity foundation, about 2,500 children with Down syndrome are born in Russia every year.
Klinefelter syndrome
Another chromosomal disorder. For about every 500 newborn boys, there is one with this pathology. Klinefelter syndrome usually appears after puberty. Men suffering from this syndrome are infertile. In addition, they are characterized by gynecomastia - an increase in mammary gland with hypertrophy of glands and adipose tissue.
The syndrome got its name in honor of the American doctor Harry Klinefelter, who first described the clinical picture of the pathology in 1942. Together with endocrinologist Fuller Albright, he found out that if normally women have a pair of sex chromosomes XX, and men have XY, then with this syndrome in men there are from one to three additional X chromosomes.
Colorblindness
Or color blindness. It is hereditary, much less often acquired. Expressed in the inability to distinguish one or more colors.
Color blindness is associated with the X chromosome and is transmitted from a mother, the owner of a “broken” gene, to her son. Accordingly, up to 8% of men and no more than 0.4% of women suffer from color blindness. The fact is that in men, the “marriage” in the only X chromosome is not compensated for, since, unlike women, they do not have a second X chromosome.
Hemophilia
Another disease that sons inherit from their mothers. The story of the descendants of the English Queen Victoria from the Windsor dynasty is widely known. Neither she herself nor her parents suffered from this serious disease associated with blood clotting disorders. Presumably, the gene mutation occurred spontaneously, due to the fact that Victoria’s father was already 52 years old at the time of her conception.
Victoria's children inherited the fatal gene. Her son Leopold died of hemophilia at age 30, and two of her five daughters, Alice and Beatrice, were carriers of the ill-fated gene. One of Victoria's most famous hemophiliac descendants is her granddaughter's son, Tsarevich Alexei, the only son of the last Russian Emperor, Nicholas II.
Cystic fibrosis
A hereditary disease that manifests itself in disruption of the exocrine glands. It is characterized increased sweating, the secretion of mucus, which accumulates in the body and prevents the child from developing, and, most importantly, prevents the full functioning of the lungs. Death due to respiratory failure is likely.
According to the Russian branch of the American chemical and pharmaceutical corporation Abbott, average duration The lifespan of patients with cystic fibrosis is 40 years in European countries, 48 years in Canada and the USA, and 30 years in Russia. A well-known example is the French singer Gregory Lemarchal, who died at the age of 23. Presumably, Frederic Chopin also suffered from cystic fibrosis, and died as a result of lung failure at the age of 39.
A disease mentioned in ancient Egyptian papyri. Characteristic symptom migraines - episodic or regular severe attacks headache in one side of the head. The Roman physician of Greek origin, Galen, who lived in the 2nd century, called the disease hemicrania, which translates as “half a head.” The word “migraine” comes from this term. In the 90s In the 20th century, it was found that migraine is predominantly caused by genetic factors. A number of genes have been discovered that are responsible for the inheritance of migraine.
Genetic diseases- these are diseases that arise in humans due to chromosomal mutations and defects in genes, that is, in the hereditary cellular apparatus. Damage to the genetic apparatus leads to serious and varied problems - hearing loss, visual impairment, delayed psycho-physical development, infertility and many other diseases.
Each cell of the body has a cell nucleus, the main part of which is made up of chromosomes. A set of 46 chromosomes is a karyotype. 22 pairs of chromosomes are autosomes, and the last 23 pair are sex chromosomes. These are the sex chromosomes that differentiate a man and a woman from each other.
Everyone knows that women have XX chromosomes, and men have XY chromosomes. When a new life arises, the mother passes on the X chromosome, and the father - either X or Y. It is with these chromosomes, or rather with their pathology, that genetic diseases are associated.
The gene can mutate. If it is recessive, then the mutation can be passed on from generation to generation without manifesting itself in any way. If the mutation is dominant, then it will definitely manifest itself, so it is advisable to protect your family by learning about the potential problem in time.
More and more hereditary pathologies are being discovered every year. More than 6,000 names of genetic diseases are already known; they are associated with both quantitative and qualitative changes in the genetic material. According to the World Health Organization, approximately 6% of children suffer from hereditary diseases.
The most unpleasant thing is that genetic diseases can appear only after several years. Parents rejoice healthy baby, not suspecting that the children are sick. For example, some hereditary diseases can manifest themselves at the age when the patient himself has children. And half of these children may be doomed if the parent carries a dominant pathological gene.
But sometimes it is enough to know that the child’s body is not able to absorb a certain element. If parents are warned about this in time, then in the future, simply avoiding products containing this component, you can protect the body from manifestations of a genetic disease.
Therefore, it is very important that when planning a pregnancy, a test is done for genetic diseases. If the test shows the likelihood of transmitting the mutated gene to the unborn child, then in German clinics they can carry out gene correction during artificial insemination. Tests can also be done during pregnancy.
In Germany you may be offered innovative technologies the latest diagnostic developments that can dispel all your doubts and suspicions. About 1,000 genetic diseases can be detected before a child is born.
We will look at two groups of genetic diseases (actually there are more)
1. Diseases with a genetic predisposition.
Such diseases can manifest themselves under the influence external factors environment and are highly dependent on individual genetic predisposition. Some diseases may appear in older people, while others may appear unexpectedly and early. So, for example, swipe on the head can provoke epilepsy, taking an indigestible product can cause violent allergies, etc.
2. Diseases that develop in the presence of a dominant pathological gene.
Such genetic diseases are passed on from generation to generation. For example, muscular dystrophy, hemophilia, six-fingered, phenylketonuria.
Which families first need to attend genetic consultations and identify the risk of hereditary diseases in their offspring?
1. Consanguineous marriages.
2. Infertility of unknown etiology.
3. Age of parents. Considered a risk factor if to the expectant mother more than 35 years old, and my father is more than 40 (according to some sources, more than 45). With age, more and more damage appears in the reproductive cells, which increases the risk of having a baby with a hereditary pathology.
4. Hereditary family diseases, that is, similar diseases in two or more family members. There are diseases with bright severe symptoms and the parents have no doubt that this is a hereditary disease. But there are signs (microanomalies) that parents do not pay due attention to. For example, an unusual shape of the eyelids and ears, ptosis, coffee-colored spots on the skin, a strange smell of urine, sweat, etc.
5. Complicated obstetric history - stillbirth, more than one spontaneous miscarriage, missed pregnancies.
6. Parents are representatives of a small nationality or come from one small locality (in this case, there is a high probability of consanguineous marriages)
7. Impact of unfavorable household or professional factors on one of the parents (calcium deficiency, insufficient protein nutrition, work in a printing house, etc.)
8. Poor environmental conditions.
9. Use of drugs with teratogenic properties during pregnancy.
10. Diseases, especially viral etiology (rubella, chicken pox) suffered by a pregnant woman.
11. Don't healthy image life. Constant stress, alcohol, smoking, drugs, poor nutrition can cause damage to genes, since the structure of chromosomes under the influence of unfavorable conditions can change throughout life.
In Germany, the diagnosis of genetic diseases is highly effective, since all known high-tech methods and absolutely all the capabilities of modern medicine (DNA analysis, DNA sequencing, genetic passport, etc.) are used to determine potential hereditary problems. Let's look at the most common ones.
1. Clinical and genealogical method.
This method is important condition qualitative diagnosis of genetic disease. What does it include? First of all, a detailed interview with the patient. If there is a suspicion of a hereditary disease, then the survey concerns not only the parents themselves, but also all relatives, that is, complete and thorough information is collected about each family member. Subsequently, a pedigree is compiled indicating all the signs and diseases. This method ends genetic analysis, on the basis of which a correct diagnosis is made and optimal therapy is selected.
2. Cytogenetic method.
Thanks to this method, diseases that arise due to problems in the cell's chromosomes are determined. The cytogenetic method examines the internal structure and arrangement of chromosomes. This is very simple technique- a scraping is taken from the mucous membrane of the inner surface of the cheek, then the scraping is examined under a microscope. This method is carried out with parents and family members. A type of cytogenetic method is molecular cytogenetic, which allows you to see the smallest changes in the structure of chromosomes.
3. Biochemical method.
This method, by examining the mother’s biological fluids (blood, saliva, sweat, urine, etc.), can determine hereditary diseases based on metabolic disorders. One of the most famous genetic diseases associated with metabolic disorders is albinism.
4. Molecular genetic method.
This is the most progressive method currently used to identify monogenic diseases. It is very accurate and detects pathology even in the nucleotide sequence. Thanks to this method, it is possible to determine a genetic predisposition to the development of oncology (cancer of the stomach, uterus, thyroid gland, prostate, leukemia, etc.) Therefore, it is especially indicated for persons whose close relatives suffered from endocrine, mental, oncological and vascular diseases.
In Germany, to diagnose genetic diseases, you will be offered the full range of cytogenetic, biochemical, molecular genetic studies, prenatal and postnatal diagnostics, plus neonatal screening of the newborn. Here you can take about 1000 genetic tests that are approved for clinical application on the territory of the country.
Prenatal diagnosis provides great opportunities for identifying genetic diseases.
Prenatal diagnosis includes studies such as
Screening methods such as triple test, fetal echocardiography, and determination of alpha-fetoprotein are also used in diagnosis.
Ultrasound imaging of the fetus in 3D and 4D dimensions can significantly reduce the birth of babies with developmental defects. All these methods have a low risk of side effects and do not adversely affect the course of pregnancy. If a genetic disease is detected during pregnancy, the doctor will suggest certain individual tactics for managing the pregnant woman. In the early stages of pregnancy, German clinics can offer gene correction. If gene correction is carried out in time in the embryonic period, then some genetic defects can be corrected.
Neonatal newborn screening identifies the most common genetic diseases in an infant. Early diagnosis allows you to understand that the child is sick even before the first signs of illness appear. Thus, the following can be identified hereditary diseases- hypothyroidism, phenylketonuria, maple syrup disease, adrenogenital syndrome and others.
If these diseases are detected in time, the chance of curing them is quite high. High-quality neonatal screening is also one of the reasons why women fly to Germany to give birth to a child here.
Until recently, genetic diseases were not treated; it was considered impossible, and therefore hopeless. Therefore, the diagnosis of a genetic disease was regarded as a death sentence, and at best, one could only count on symptomatic treatment. Now the situation has changed. Progress is noticeable, there are positive results treatment, moreover, science is constantly discovering new and effective ways treatment of hereditary diseases. And although many hereditary diseases cannot be cured today, geneticists are optimistic about the future.
Treatment of genetic diseases is a very complex process. It is based on the same principles of influence as any other disease - etiological, pathogenetic and symptomatic. Let's look briefly at each.
1. Etiological principle of influence.
The etiological principle of influence is the most optimal, since treatment is aimed directly at the causes of the disease. This is achieved using methods of gene correction, isolating the damaged part of DNA, cloning it and introducing it into the body. At the moment, this task is very difficult, but for some diseases it is already feasible
2. Pathogenetic principle of influence.
Treatment is aimed at the mechanism of development of the disease, that is, it changes the physiological and biochemical processes in the body, eliminating defects caused by the pathological gene. As genetics evolves pathogenetic principle the impact is expanding, and for different diseases, new ways and possibilities for correcting broken links will be found every year.
3. Symptomatic principle of influence.
According to this principle, treatment of a genetic disease is aimed at relieving pain and other unpleasant phenomena and prevents further progression of the disease. Symptomatic treatment is always prescribed; it can be combined with other methods of treatment, or it can be an independent and sole treatment. This is the prescription of painkillers, sedatives, anticonvulsants and other medications. The pharmaceutical industry is now very developed, so the spectrum medicines, used for the treatment (or rather, for the relief of manifestations) of genetic diseases is very wide.
In addition to drug treatment symptomatic treatment include the use of physiotherapeutic procedures - massage, inhalations, electrotherapy, balneotherapy, etc.
Sometimes surgical treatment is used to correct deformities, both external and internal.
Geneticists in Germany already have extensive experience in treating genetic diseases. Depending on the manifestation of the disease and individual parameters, the following approaches are used:
Of course, treatment of genetic diseases takes a long time and is not always successful. But the number of new approaches to therapy is growing every year, so doctors are optimistic.
Doctors and scientists around the world place special hopes on gene therapy, thanks to which it is possible to introduce high-quality genetic material into the cells of a sick organism.
Gene correction consists of the following stages:
Gene correction requires great caution, since science does not yet have complete information about the functioning of the genetic apparatus.
There are many classifications of genetic diseases, they are arbitrary and differ in the principle of construction. Below we provide a list of the most common genetic and hereditary diseases:
In this section we will go into detail about each disease and tell you how some of them can be cured. But it is better to prevent genetic diseases than to treat them, especially since modern medicine does not know how to cure many diseases.
Genetic diseases are a group of diseases that are very heterogeneous in their clinical manifestations. Basic external manifestations genetic diseases:
Conversation in genetic consultation and prenatal diagnosis can prevent severe hereditary diseases transmitted at the gene level. The main goal of genetic counseling is to identify the degree of risk of a genetic disease in a newborn.
In order to receive quality consultation and advice on further actions, you need to be serious about communicating with your doctor. Before the consultation, you need to responsibly prepare for the conversation, remember the illnesses your relatives suffered, describe all health problems and write down the main questions to which you would like answers.
If the family already has a child with an anomaly, with congenital malformations, take his photographs. It is imperative to talk about spontaneous miscarriages, cases of stillbirth, and how the pregnancy went (is going).
A genetic consultation doctor will be able to calculate the risk of having a baby with a severe hereditary pathology (even in the future). When can we talk about a high risk of developing a genetic disease?
Doctors advise considering a risk of about or above 20% as a reason to terminate the pregnancy or (if one does not exist yet) as a contraindication to conception. But the final decision is made, of course, by the married couple.
The consultation may take place in several stages. When diagnosing a genetic disease in a woman, the doctor develops management tactics before pregnancy and, if necessary, during pregnancy. The doctor talks in detail about the course of the disease, life expectancy for this pathology, all the possibilities of modern therapy, the price component, and the prognosis of the disease. Sometimes gene correction during artificial insemination or during the period embryonic development allows you to avoid manifestations of the disease. New methods are being developed every year gene therapy and prevention of hereditary diseases, so the chances of curing genetic pathology are constantly increasing.
In Germany, methods of combating gene mutations using stem cells, new technologies for the treatment and diagnosis of genetic diseases are being considered.
This problem is long-standing and very serious, although no more than five percent of newborn children 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. Diseases such as cancer can be hereditary diabetes mellitus, heart defects and many other diseases. Congenital diseases may result from abnormal development of genes or chromosomes. Sometimes it only takes a few abnormal cells to appear for a person to subsequently develop a malignant disease.
As for the medical term “genetic diseases”, it applies 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. This destructive phenomenon occurs as a result of improper maturation of the egg and sperm. These diseases are sometimes called chromosomal. These include such serious illnesses as Down syndrome, Klinefelter syndrome, Edwards syndrome and others. Modern medicine almost 4 thousand are known various diseases arising on the basis of genetic abnormalities. Another interesting fact is that 5 percent of people have at least one defective gene in their body, but at the same time they are completely healthy people.
Terminology in the article
A gene is the initial unit of heredity, which is part of a DNA molecule that influences the formation of protein in the body, and therefore the signs of the state of the body. Genes are presented in binary form, that is, one half is transmitted from the mother, and the other from the father.
Deoxyribonucleic acid (DNA) is a substance found in every cell. It carries 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 state of the body during its development.
Mutations are persistent and irreversible changes in genetic information about the organism.
Quite common are monogenic diseases, in which only one gene responsible for a certain function of the body is damaged. Due to the fact that there are many such diseases, medicine has adopted a certain classification of them, which looks like this.
Autosomal dominant diseases.
This group includes diseases that occur when there is only one copy of a defective gene. That is, only one of the patient’s parents is sick. Thus, it becomes clear that the offspring of such a sick person have a 50% chance of inheriting the disease. This group of diseases includes diseases such as Marfan syndrome, Huntington's disease and others.
Autosomal recessive diseases.
This group includes diseases that occur due to the presence of two defective copies of a gene. In this case, those who gave 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 risk of having a sick child is 25%. This group of diseases includes diseases such 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 occur due to the presence of defective genes on the female sex X chromosome. Boys are more likely to suffer from such diseases than girls. Although a boy born from a sick father may not pass the disease on to his offspring. As for girls, they will all necessarily have a defective gene. If the mother is sick, then the probability of inheriting her disease is the same for boys and girls and is 50%.
X-linked recessive diseases.
This group includes those diseases that are caused by mutations of genes located on the X chromosome. IN in this case Boys are at greater risk of inheriting the disease than girls. Also, a sick boy may not subsequently pass the disease on to his children. Girls will also have one copy of the defective gene in any case. If a mother is a carrier of a defective gene, then she has a 50% chance of giving birth to a sick son or a daughter who will become a carrier of such a gene. This group of diseases includes diseases such 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 external conditions. The heredity of these diseases is manifested only relatively, although the diseases often have familial characteristics. These are diabetes, heart disease and some others.
Chromosomal diseases.
This includes those diseases that arise due to a violation of the number and structure of chromosomes. If such signs are present, women often experience miscarriages and undeveloped pregnancies. Children of such women are born with both mental and physical abnormalities. Such cases, alas, occur quite often, namely in one out of twelve fertilizations. The results of such sad statistics are not visible due to termination of pregnancy at a certain stage of fetal development. As for born children, statistics say that one out of one hundred and fifty newborns is born with this disease. Already in the first trimester of pregnancy, half of women with chromosomal diseases of the fetus experience miscarriages. This indicates that the treatment is ineffective.
Before talking about the prevention of hereditary and congenital diseases, it is worth spending a little time on issues related to polygenic or multifactorial diseases. These diseases occur in adults and often cause concern about the feasibility of having offspring and the likelihood of diseases passing on from parents to children. The most common diseases in this group are such diseases.
Diabetes mellitus types 1 and 2 .
This disease has partially hereditary characteristics. Type 1 diabetes can also develop due to viral infection or due to long-term nervous disorders. Examples have been noted where diabetes-1 arose as a result of allergic reaction to aggressive external environment and even on medical supplies. Some people with diabetes are carriers of a gene that is responsible for the likelihood of developing the disease in childhood or adolescence. As for type 2 diabetes, the hereditary nature of its occurrence is clearly visible. The highest probability of developing type 2 diabetes is already in the first generation of the carrier’s descendants. That is, his own children. This probability is 25%. However, if the husband and wife are also relatives, then their children will necessarily inherit parental diabetes. 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. As arterial hypertension develops, at least fifty genes take part in the disease and their number grows over time. 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 body’s hereditary predisposition to arterial hypertension, a healthy lifestyle plays a huge role in treatment.
Violation fat metabolism.
This disease is the result of the influence of genetic factors together with a person’s lifestyle. Many genes are responsible for metabolism in the body, for the formation of fat mass and for the strength of a person’s appetite. Failure of just one of them can lead to the appearance of various diseases. Externally, a disorder of fat metabolism manifests itself in the form of obesity in the patient’s body. Among obese people, fat metabolism is impaired in only 5% of them. This phenomenon can be observed en masse in some ethnic groups, which confirms the genetic origin of this disease.
Malignant neoplasms.
Cancerous tumors do not appear as a result of heredity, but haphazardly and one might even say by chance. Nevertheless, isolated cases have been recorded in medicine when cancerous tumors arose precisely as a result of heredity. These are mainly cancers of the breast, ovaries, colon and blood. The reason for this is a congenital mutation of the VYACA1 gene.
Mental development disorder.
The most common cause of mental retardation is hereditary factor. Parents of a mentally retarded child are often carriers of a number of mutant genes. Often, the interaction of individual genes is disrupted or disturbances in the number and structure of chromosomes are observed. Characteristic symptoms include Down syndrome, fragile X syndrome and phenylketonuria.
Autism.
This disease is associated with impaired brain functionality. 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 divide 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 disease at the stage of planning conception. It also includes measures for diagnosing fetal development using systematic examinations of a pregnant woman.
When planning a pregnancy, in order to prevent hereditary diseases, it is worth contacting the regional clinic, where the “Family and Marriage” database stores archival data on the health of the spouses’ ancestors. As for medical genetic consultation, it is necessary if the spouses have chromosomal changes, hereditary diseases, and, of course, if abnormal development a fetus or an already born child. In addition, such consultation must be obtained if the husband and wife are in family ties. Consultation is extremely necessary for those couples who have previously experienced miscarriages or children who were stillborn. It will also 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 is made of the pedigree of both spouses, based on the medical data available in the archive on the health of previous generations of the husband and wife. In this case, it is possible to identify with almost absolute accuracy whether there is a likelihood of a hereditary disease occurring in the unborn child, or whether there is none. Before going for a consultation, spouses must ask their parents and relatives in as much detail as possible about the diseases that occurred in previous generations of the family. If there are hereditary diseases in the family history, then you must tell your doctor about it. This will make it easier for him to determine the necessary preventive measures.
Sometimes at the stage of primary prevention it is necessary to analyze the state of the chromosome set. This analysis is performed on both parents, since the child will inherit half of the chromosome from mom and dad. Unfortunately completely healthy people may be carriers of balanced chromosomal rearrangements and not even suspect 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 the spouses have rearrangements in the chromosome set, then during pregnancy with the help of PD it is possible to prevent the birth of an unhealthy child.
As part of the primary prevention of congenital anomalies of a child’s nervous system, a widely used method is the administration of folic acid, which is a solution of vitamins in water. Before pregnancy, a sufficient amount of folic acid enters the woman’s body during good nutrition. If she adheres to any diet, then, of course, the supply 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 ensure such an increase through diet alone.
By the way, this is the only vitamin that during pregnancy should enter the body in greater quantities than before pregnancy. It is possible to satisfy the complete need of a pregnant woman’s body for folic acid only due to 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 child’s central nervous system by three times! Usually the doctor prescribes four standard tablets per day. If the first child had some kind of deviation in the development of the central nervous system, and the woman decided to give birth again, then in this case 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 applied even in the case 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 discovered, 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 this, the parents decide for themselves whether it is worth giving birth to a child or whether it would be better and more humane to terminate the pregnancy in 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 conduct a blood test of the mother and conduct ultrasound diagnostics of her body and the fetus. IN lately Doctors have mastered the technology of taking blood tests from the fetus. The sample is taken from the mother's placenta, into which fetal blood penetrates. This process is quite complicated, but also quite effective.
Maternal blood testing is usually done at the end of the first - beginning of the second trimester of pregnancy. If two or three substances are present in the blood in abnormal quantities, then this may be a sign of the presence of a hereditary disease. In addition, at the end of the first trimester of pregnancy, human chorionic gonadotropin is determined in the mother. This is a pregnancy hormone, which in a woman’s body is produced by the placenta and in turn produces serum protein A. In the second trimester of pregnancy, an analysis is done for the content of hCG, alpha-fetoprotein, and unbound (free) estriol.
A set of such measures in world medicine is called a “triple panel”, and the overall 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 childbirth. HCG supports the production in the ovaries of hormones necessary for normal course 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 syndrome, the content of the hormone in the mother’s blood serum is significantly increased.
Whey protein A is produced in the mother's body in the tissue of the placenta. If the fetus has chromosomal disease, then the amount of protein will be underestimated. It should be noted that such changes can only be recorded from the tenth to fourteenth week of pregnancy. Subsequently, the level of protein in the mother’s blood serum returns to normal.
Alpha fetoprotein (AFP) is produced already 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 of congenital defects of the central nervous system, kidneys, or anterior abdominal wall. It is known that in cases of cancer, this protein is found in the blood serum of both adults and children. As the fetus develops, this protein passes from the fetal kidneys into 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 is not of decisive importance from the point of view of diagnostic accuracy. 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 this time, from the point of view of diagnostic accuracy, it makes no sense to determine this protein. If the fetus has birth defect central nervous system or anterior abdominal wall, then the level of AFP in the mother’s blood serum will be significantly higher than normal. If the fetus suffers from Down or Edwards syndrome, then, on the contrary, this indicator will be lower than 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 under normal conditions also increases progressively. If the fetus has a chromosomal disease, then the level of unbound estriol in the mother’s body is significantly lower than that required for normal pregnancy, norms. Studying the level of the hormone estriol allows one 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 complex.
Carrying out biochemical screening is very important procedure. In addition, this method has a number of advantages. It does not require surgical intervention in the mother’s body and is not technologically complex process. At the same time, effectiveness this study very high. However, this method is not without its drawbacks. In particular, it allows you to determine only the degree of probability of the occurrence of a congenital disease, and not the fact of its presence. In order to accurately identify this presence, additional diagnostic testing is required. The saddest thing is that the results of biochemical screening can be absolutely normal, but the fetus has a chromosomal disorder. This technique requires the most accurate determination of the date of fertilization and is not suitable for studying multiple pregnancies.
Ultrasound examination
Devices for ultrasound diagnostics are constantly being improved. Modern models allow you to view the fetus even in a three-dimensional image format. These devices have been used in medicine for quite a long time and during this time it has been fully proven that they do not have any effect. negative impact neither on the health of the fetus nor on the health of the mother. According to medical standards in force in Russian Federation, ultrasound examination of pregnant women is carried out three times. The first time this is done during the period 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 describes in detail the condition of the mother’s placenta.
Using an ultrasound, the doctor determines the thickness of the collar space along the back surface of the fetal neck. If the thickness of this part of the fetal 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 syndrome. In this case, the woman is prescribed additional examination. At this stage of pregnancy, the doctor checks the degree of development of the fetus's nasal bone. If the fetus has a chromosomal disease, the nasal bone will be underdeveloped. With this detection, additional examination of the mother and fetus is also required.
During the second study, at 10-24 weeks of pregnancy, 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 during the period 20 - 24 weeks of pregnancy. Moreover, the remaining half may in fact 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.
It is understandable that parents are impatient to find out who will be born to them, a girl or a boy. It should be said that conducting research just for the sake of curiosity is not recommended, especially since in five percent of cases it is not possible to accurately determine the sex of the child.
Very often, the doctor prescribes repeated examinations for pregnant women, and this scares many. However, there is no need to panic because only 15% of repeat examinations are associated with the presence of signs of abnormal fetal development. Of course, in this case, the doctor must tell both parents about this. In other cases, repeated 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 research process determines the rate of fetal development and identifies signs of defects that are characteristic of late manifestation. If any pathology is detected, the pregnant woman is asked to have a tissue sample of the fetus or placenta analyzed.
Chorionic villus (placenta) biopsy can be done between 8 and 12 weeks of pregnancy. This procedure is performed on an outpatient basis. No more than five to ten milligrams of tissue is taken for analysis. Such an insignificant amount is quite enough to analyze 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 taking amniotic fluid for analysis. They begin to be produced in the body of a pregnant woman soon after conception. The amniotic fluid contains fetal cells. During analysis, these cells can be isolated and examined. Typically, this test is performed between 16 and 20 weeks of pregnancy. In this case, no more than 20 milliliters of water is taken, which is absolutely safe for the woman and the fetus. Another method of “early amniocentesis” is also used, which can be performed at the end of the first trimester of pregnancy. Lately it has been rarely used. This is due to the fact that in recent years, cases of limb defects in the fetus have become more frequent.
Cordocentesis is another name for intrauterine umbilical cord puncture. This technique is used to obtain a fetal blood sample for further laboratory research. This test is usually performed between 20 and 24 weeks of pregnancy. The amount of blood required for a full 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 such studies, one to two percent of women have a termination of pregnancy. Thus, these tests are best performed when the likelihood of congenital diseases in the fetus is too high. At the same time, the importance of these tests cannot be denied, since they make it possible to identify even one altered gene in the fetal body. And yet invasive methods are gradually becoming a thing of the past, and are being replaced by new technologies. They allow fetal cells to be isolated from the mother's blood.
Thanks to the development of a method such as in vitro fertilization in the treatment of infertility, it has become possible to carry out preimplantation diagnostics. Its essence is as follows. The egg is artificially fertilized in a laboratory and placed in an incubator for a certain time. Here cell division occurs, that is, the formation of an embryo essentially begins. It is at this time that you can take one cell for research and conduct a full DNA analysis. In this way, it is possible to find out exactly how the fetus will subsequently develop, including from the perspective 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 parents and sometimes relatives of the unborn baby about this. It often happens that there is no hope for correction of any pathology identified in the fetal body, 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, they need to take into account that the tragedy of termination of pregnancy is not commensurate with the tragedy that will happen at the birth of a defective child.
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All genetic diseases, of which several thousand are known today, are caused by anomalies in the genetic material (DNA) of a person.
Genetic diseases can be associated with a mutation of one or more genes, with a violation of the arrangement, absence or duplication of entire chromosomes (chromosomal diseases), as well as with maternally transmitted mutations in the genetic material of mitochondria (mitochondrial diseases).
More than 4,000 diseases associated with a defect in one gene (single gene disorders) have been described.
It is also known that some genetic diseases arose in us as an attempt by the body to resist environment. Sickle cell anemia, according to modern data, originated in Africa, where for many thousands of years malaria was a real scourge of humanity. In sickle cell anemia, people have a mutation in their red blood cells that makes the host resistant to Plasmodium falciparum.
Today, scientists have developed tests for hundreds of genetic diseases. We can test for cystic fibrosis, Down syndrome, fragile X syndrome, hereditary thrombophilias, Bloom's syndrome, Canavan disease, Fanconi anemia, familial dysautonomia, Gaucher disease, Niemann-Pick disease, Klinefelter syndrome, thalassemias and many other diseases.
Known diseases include thrombophilia associated with the Leiden mutation (factor V Leiden). There are other genetic clotting disorders, including prothrombin deficiency (factor II), protein C deficiency, protein S deficiency, antithrombin III deficiency, and others.
Everyone has heard about hemophilia - a hereditary coagulation disorder that causes dangerous hemorrhages in internal organs, muscles, joints, abnormal menstrual bleeding is observed, and any minor injury can lead to irreparable consequences due to the body’s inability to stop the bleeding. The most common is hemophilia A (coagulation factor VIII deficiency); Hemophilia B (factor IX deficiency) and hemophilia C (factor XI deficiency) are also known.
There is also a very common von Willebrand disease, in which spontaneous bleeding is observed due to reduced level factor VIII. The disease was described in 1926 by Finnish pediatrician von Willebrand. American researchers believe that 1% of the world's population suffers from it, but in most of them the genetic defect does not cause serious symptoms(for example, women may only have heavy periods). Clinically significant cases, in their opinion, are observed in 1 person in 10,000, that is, 0.01%.
Modern treatment is aimed at combating the symptoms of the disease. Huntington's disease usually begins to manifest itself at the age of 30-40, and until then a person may have no idea about his fate. Less commonly, the disease begins to progress in childhood. It is an autosomal dominant disorder - if one parent has the defective gene, the child has a 50% chance of getting it.
Treatment includes pain medications, folic acid to support hematopoiesis, blood transfusions, dialysis, and hydroxyurea to reduce the frequency of episodes. Sickle cell anemia occurs primarily in people of African and Mediterranean heritage, as well as in South and Central America.
In addition to those listed above, there are many other genetic diseases. Today there are no radical treatments for them, but gene therapy has enormous potential. Many diseases, especially when diagnosed early, can be successfully controlled, and patients are able to live full, productive lives.
