What can be genetic diseases. Genetic diseases that are inherited. Medical genetic testing. Types of Genetic Diseases

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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, misalignment, absence or duplication of entire chromosomes (chromosomal diseases), as well as maternally transmitted mutations in the genetic material of mitochondria (mitochondrial diseases).

More than 4,000 diseases associated with single gene disorders have been described.

A little about genetic diseases

It is also known that some genetic diseases arose in us as an attempt by the body to resist the environment. Sickle cell anemia, according to modern data, originated in Africa, where malaria has been a real scourge of mankind for many thousands of years. In sickle cell anemia, humans have a red blood cell mutation that makes the host resistant to Plasmodium malaria.

Today, scientists have developed tests for hundreds of genetic diseases. We can test for cystic fibrosis, Down syndrome, fragile X syndrome, hereditary thrombophilias, Bloom syndrome, Canavan disease, Fanconi anemia, familial dysautonomia, Gaucher disease, Niemann-Pick disease, Klinefelter syndrome, thalassemias and many other diseases.

Cystic fibrosis.

Down Syndrome.

Fragile X syndrome.

Hereditary bleeding disorders.

Among the known diseases is thrombophilia associated with the Leiden mutation (factor V Leiden). There are other genetic coagulation disorders, including prothrombin (factor II) deficiency, protein C deficiency, protein S deficiency, antithrombin III deficiency, and others.

Everyone has heard of hemophilia - a hereditary coagulation disorder in which dangerous hemorrhages occur in the 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 (deficiency of clotting factor VIII); hemophilia B (factor IX deficiency) and hemophilia C (factor XI deficiency) are also known.

There is also the very common von Willebrand disease, in which spontaneous bleeding is observed due to a reduced level of factor VIII. The disease was described in 1926 by the 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 can only have heavy menstruation). Clinically significant cases, in their opinion, are observed in 1 person per 10,000, that is, 0.01%.

Familial hypercholesterolemia.

Huntington's disease.

Modern treatment is aimed at combating the symptoms of the disease. Huntington's disease usually begins to manifest itself in 30-40 years, and before that a person may not guess about his fate. Less commonly, the disease begins to progress in childhood. This is an autosomal dominant disease - if one parent has the defective gene, then the child has a 50% chance of getting it.

Duchenne muscular dystrophy.

Becker muscular dystrophy.

Sickle cell anemia.

Treatment includes pain medications, folic acid to support hematopoiesis, blood transfusions, dialysis, and hydroxyurea to reduce the frequency of episodes. Sickle cell anemia occurs predominantly in people of African and Mediterranean ancestry, as well as in South and Central Americans.

Thalassemia.

Phenylketonuria.

Alpha-1 antitrypsin deficiency.

In addition to those listed above, there are a huge number of other genetic diseases. To date, there are no radical treatments for them, but gene therapy has huge potential. Many diseases, especially with timely diagnosis, can be successfully controlled, and patients get the opportunity to live a full, productive life.

Every healthy person has 6-8 damaged genes, but they do not disrupt cell functions and do not lead to disease, because they are recessive (non-manifested). If a person inherits two similar abnormal genes from his mother and father, he becomes ill. The probability of such a coincidence is extremely small, but it increases dramatically if the parents are relatives (that is, they have a similar genotype). For this reason, the frequency of genetic abnormalities is high in closed populations.

Each gene in the human body is responsible for the production of a specific protein. Due to the manifestation of a damaged gene, the synthesis of an abnormal protein begins, which leads to cell dysfunction and developmental defects.

The doctor can establish the risk of a possible genetic anomaly by asking you about the diseases of relatives “up to the third knee”, both on your part and on the part of your husband.

Genetic diseases are numerous and some are very rare.

List of rare hereditary diseases

Here are the characteristics of some genetic diseases.

Down syndrome (or trisomy 21)- a chromosomal disease characterized by mental retardation and impaired physical development. A disease occurs due to the presence of a third chromosome in the 21st pair (in total, a person has 23 pairs of chromosomes). It is the most common genetic disease, occurring in about one in 700 newborns. The frequency of Down syndrome increases in children born to women over 35 years of age. Patients with this disease have a special appearance and suffer from mental and physical retardation.

Turner syndrome- a disease that affects girls, characterized by the partial or complete absence of one or two X chromosomes. The disease occurs in one in 3,000 girls. Girls with this disease are usually very small and their ovaries do not function.

X-trisomy syndrome- a disease in which a girl is born with three X chromosomes. This disease occurs in an average of one in 1000 girls. The X-trisomy syndrome is characterized by a slight mental retardation and, in some cases, infertility.

Klinefelter syndrome- a disease in which the boy has one extra chromosome. The disease occurs in one boy out of 700. Patients with Klinefelter's syndrome, as a rule, are tall, there are no noticeable external developmental anomalies (after puberty, facial hair growth is difficult and the mammary glands are somewhat enlarged). Intellect in patients is usually normal, but speech disorders are common. Men with Klinefelter syndrome are usually infertile.

cystic fibrosis- a genetic disease in which the functions of many glands are impaired. Cystic fibrosis only affects Caucasians. Approximately one in 20 white people has one damaged gene that, if manifested, can cause cystic fibrosis. The disease occurs when a person receives two of these genes (from the father and from the mother). In Russia, cystic fibrosis, according to various sources, occurs in one newborn out of 3500-5400, in the USA - in one out of 2500. With this disease, the gene responsible for the production of a protein that regulates the movement of sodium and chlorine through cell membranes is damaged. There is dehydration and an increase in the viscosity of the secretion of the glands. As a result, a thick secret blocks their activity. In patients with cystic fibrosis, protein and fat are poorly absorbed, as a result, growth and weight gain are greatly slowed down. Modern methods of treatment (taking enzymes, vitamins and a special diet) allow half of the patients with cystic fibrosis to live more than 28 years.

Hemophilia- a genetic disease characterized by increased bleeding due to a deficiency of one of the blood coagulation factors. The disease is inherited through the female line, while it affects the vast majority of boys (an average of one in 8500). Hemophilia occurs when the genes responsible for the activity of blood clotting factors are damaged. With hemophilia, frequent hemorrhages in the joints and muscles are observed, which can ultimately lead to their significant deformation (that is, to a person's disability). People with hemophilia should avoid situations that could lead to bleeding. Patients with hemophilia should not take drugs that reduce blood clotting (for example, aspirin, heparin, and some painkillers). To prevent or stop bleeding, the patient is given a plasma concentrate containing a large amount of the missing clotting factor.

Tay Sachs disease- a genetic disease characterized by the accumulation in the tissues of phytanic acid (a product of the breakdown of fats). The disease occurs mainly among Ashkenazi Jews and Canadians of French origin (in one newborn in 3600). Children with Tay-Sachs disease are retarded from an early age, then they become paralyzed and blind. As a rule, patients live up to 3-4 years. There are no treatments for this disease.

Today, gynecologists advise all women to plan their pregnancy. After all, in this way many hereditary diseases can be avoided. This is possible with a thorough medical examination of both spouses. There are two points in the question of hereditary diseases. The first is a genetic predisposition to certain diseases, which manifests itself already with the maturation of the child. So, for example, diabetes mellitus, which one of the parents suffers from, can manifest itself in children in adolescence, and hypertension - after 30 years. The second point is directly genetic diseases with which the child is born. They will be discussed today.

The most common genetic diseases in children: description

The most common hereditary disease of a baby is Down syndrome. It occurs in 1 case out of 700. A neonatologist makes a diagnosis in a child while the newborn is in the hospital. In Down's disease, the children's karyotype contains 47 chromosomes, that is, an extra chromosome is the cause of the disease. You should know that girls and boys are equally susceptible to this chromosomal pathology. Visually, these are children with a specific facial expression, lagging behind in mental development.

Shereshevsky-Turner disease is more common in girls. And the symptoms of the disease appear at the age of 10-12: patients are not tall, the hair on the back of the head is low-set, and at 13-14 they do not have puberty and there are no periods. In these children, there is a slight lag in mental development. The leading symptom of this hereditary disease in an adult woman is infertility. The karyotype for this disease is 45 chromosomes, that is, one chromosome is missing. The prevalence of Shereshevsky-Turner disease is 1 case per 3000. And among girls up to 145 centimeters tall, it is 73 cases per 1000.

Only males have Klinefelter's disease. This diagnosis is established at the age of 16-18 years. Signs of the disease - high growth (190 centimeters and even higher), slight mental retardation, disproportionately long arms. The karyotype in this case is 47 chromosomes. A characteristic sign for an adult male is infertility. Kleinfelter's disease occurs in 1 in 18,000 cases.

Manifestations of a fairly well-known disease - hemophilia - are usually observed in boys after one year of life. Mostly representatives of the strong half of humanity suffer from pathology. Their mothers are only carriers of the mutation. Blood clotting disorder is the main symptom of hemophilia. Often this leads to the development of severe joint damage, such as hemorrhagic arthritis. With hemophilia, as a result of any injury with a cut in the skin, bleeding begins, which for a man can be fatal.

Another severe hereditary disease is cystic fibrosis. Usually, children under one and a half years old need to be diagnosed to identify this disease. Its symptoms are chronic inflammation of the lungs with dyspeptic symptoms in the form of diarrhea, followed by constipation with nausea. The frequency of the disease is 1 case per 2500.

Rare hereditary diseases in children

There are also genetic diseases that many of us have not heard of. One of them appears at the age of 5 years and is called Duchenne muscular dystrophy.

The carrier of the mutation is the mother. The main symptom of the disease is the replacement of skeletal striated muscles with connective tissue that is incapable of contraction. In the future, such a child will face complete immobility and death in the second decade of life. To date, there is no effective therapy for Duchenne myodystrophy, despite many years of research and the use of genetic engineering.

Another rare genetic disease is osteogenesis imperfecta. This is a genetic pathology of the musculoskeletal system, which is characterized by deformation of the bones. Osteogenesis is characterized by a decrease in bone mass and their increased fragility. There is an assumption that the cause of this pathology lies in a congenital disorder of collagen metabolism.

Progeria is a rather rare genetic defect, which is expressed in premature aging of the body. There are 52 cases of progeria in the world. Up to six months, children are no different from their peers. Further, their skin begins to wrinkle. Symptoms of senility appear in the body. Children with progeria usually do not live beyond the age of 15. The disease is caused by gene mutations.

Ichthyosis is a hereditary skin disease that occurs as a dermatosis. Ichthyosis is characterized by a violation of keratinization and is manifested by scales on the skin. The cause of ichthyosis is also a gene mutation. The disease occurs in one case in several tens of thousands.

Cystinosis is a disease that can turn a person into stone. The human body accumulates too much cystine (an amino acid). This substance turns into crystals, causing hardening of all body cells. The man gradually turns into a statue. Usually such patients do not live up to 16 years. The peculiarity of the disease is that the brain remains intact.

Cataplexy is a disease that has strange symptoms. At the slightest stress, nervousness, nervous tension, all the muscles of the body suddenly relax - and the person loses consciousness. All his experiences end in fainting.

Another strange and rare disease is extrapyramidal system syndrome. The second name of the disease is the dance of St. Vitus. Her attacks overtake a person suddenly: his limbs and facial muscles twitch. Developing, the syndrome of the extrapyramidal system causes changes in the psyche, weakens the mind. This disease is incurable.

Acromegaly has another name - gigantism. The disease is characterized by a high growth of a person. And the disease is caused by excessive production of somatotropin growth hormone. The patient always suffers from headaches, drowsiness. Acromegaly today also has no effective treatment.

All these genetic diseases are difficult to treat, and more often they are completely incurable.

How to identify a genetic disease in a child

The level of today's medicine makes it possible to prevent genetic pathologies. To do this, pregnant women are encouraged to undergo a set of studies to determine heredity and possible risks. In simple words, genetic analyzes are done to identify the propensity of the unborn baby to hereditary diseases. Unfortunately, statistics record an increasing number of genetic abnormalities in newborns. And practice shows that most genetic diseases can be avoided by curing them before pregnancy or by terminating a pathological pregnancy.

Doctors emphasize that for future parents, the ideal option is to analyze for genetic diseases at the stage of pregnancy planning.

Thus, the risk of transmitting hereditary disorders to the unborn baby is assessed. For this, a couple planning a pregnancy is advised to consult a geneticist. Only the DNA of future parents allows us to assess the risks of having children with genetic diseases. In this way, the health of the unborn child as a whole is also predicted.

The undoubted advantage of genetic analysis is that it can even prevent miscarriage. But, unfortunately, according to statistics, women resort to genetic analyzes most often after a miscarriage.

What influences the birth of unhealthy children

So, genetic analyzes allow us to assess the risks of having unhealthy children. That is, a geneticist can state that the risk of having a baby with Down syndrome, for example, is 50 to 50. What factors affect the health of the unborn child? Here they are:

1. The age of the parents. With age, genetic cells accumulate more and more “breakdowns”. This means that the older the father and mother, the higher the risk of having a baby with Down syndrome.
2. Close relationship of parents. Both cousins ​​and second cousins ​​are more likely to carry the same diseased genes.
3. The birth of sick children to parents or direct relatives increases the chances of having another baby with genetic diseases.
4. Chronic diseases of a family nature. If both father and mother suffer, for example, from multiple sclerosis, then the probability of the disease and the unborn baby is very high.
5. Parents belonging to certain ethnic groups. For example, Gaucher's disease, manifested by damage to the bone marrow and dementia, is more common among Ashkenazi Jews, Wilson's disease - among the peoples of the Mediterranean.
6. Unfavorable environment. If future parents live near a chemical plant, a nuclear power plant, a cosmodrome, then polluted water and air contribute to gene mutations in children.
7. Exposure to radiation on one of the parents is also an increased risk of gene mutations.

So, today, future parents have every chance and opportunity to avoid the birth of sick children. Responsible attitude to pregnancy, its planning will allow you to fully feel the joy of motherhood and fatherhood.

Especially for - Diana Rudenko

At the beginning of the 21st century, there are already more than 6 thousand types of hereditary diseases. Now in many institutes of the world a person is being studied, the list of which is huge.

The male population has more and more genetic defects and less and less chance of conceiving a healthy child. While all the reasons for the patterns of development of defects are unclear, however, it can be assumed that in the next 100-200 years science will cope with the solution of these issues.

What are genetic diseases? Classification

Genetics as a science began its research path in 1900. Genetic diseases are those that are associated with abnormalities in the human gene structure. Deviations can occur both in 1 gene and in several.

Hereditary diseases:

1. Autosomal dominant.
2. Autosomal recessive.
3. Hooked to the floor.
4. Chromosomal diseases.

The probability of an autosomal dominant deviation is 50%. With autosomal recessive - 25%. Sex-linked diseases are those caused by a damaged X chromosome.

hereditary diseases

Here are some examples of diseases, according to the above classification. So, dominant-recessive diseases include:

• Marfan syndrome.
• Paroxysmal myoplegia.
• Thalassemia.
• Otosclerosis.

Recessive:

• Phenylketonuria.
• Ichthyosis.
• Other.

Sex-linked diseases:

• Hemophilia.
• Muscular dystrophy.
• Farby disease.

Also on hearing human chromosomal hereditary diseases. The list of chromosomal abnormalities is as follows:

• Shereshevsky-Turner syndrome.
• Down Syndrome.

Polygenic diseases include:

• Dislocation of the hip (congenital).
• Heart defects.
• Schizophrenia.
• Cleft lip and palate.

The most common gene anomaly is syndactyly. That is, the fusion of fingers. Syndactyly is the most innocuous disorder and is treated with surgery. However, this deviation accompanies other more serious syndromes.

What diseases are the most dangerous

Of those listed diseases, the most dangerous hereditary human diseases can be distinguished. Their list consists of those types of anomalies where trisomy or polysomy occurs in the chromosome set, that is, when the presence of 3, 4, 5 or more is observed instead of a pair of chromosomes. There is also 1 chromosome instead of 2. All these deviations occur due to a violation of cell division.

The most dangerous human hereditary diseases:

• Edwards Syndrome.
• Spinal muscular amyotrophy.
• Patau syndrome.
• Hemophilia.
• Other diseases.

As a result of such violations, the child lives for a year or two. In some cases, the deviations are not so serious, and the child can live up to 7, 8 or even 14 years.

Down syndrome

Down syndrome is inherited if one or both parents are carriers of defective chromosomes. More specifically, the syndrome is linked to a chromosome (i.e., chromosome 21 is 3, not 2). Children with Down syndrome have strabismus, wrinkling of the neck, abnormally shaped ears, heart problems, and mental retardation. But for the life of newborns, a chromosomal anomaly does not pose a danger.

Now statistics say that out of 700-800 children, 1 is born with this syndrome. Women who want to have a baby after 35 are more likely to have such a baby. The probability is somewhere around 1 in 375. But a woman who decides to have a baby at 45 has a probability of 1 in 30.

acrocraniodysphalangia

The type of inheritance of the anomaly is autosomal dominant. The cause of the syndrome is a violation in chromosome 10. In science, this disease is called acrocraniodysphalangia, if it is simpler, then Apert's syndrome. It is characterized by such structural features of the body as:

• brachycephaly (violations of the ratio of the width and length of the skull);
• fusion of the coronal sutures of the skull, as a result of which hypertension is observed (increased blood pressure inside the skull);
• syndactyly;
• convex forehead;
• often mental retardation against the background of the fact that the skull squeezes the brain and does not allow nerve cells to grow.

Nowadays, children with Apert syndrome are given skull augmentation surgery to restore their blood pressure. And mental underdevelopment is treated with stimulants.

If there is a child in the family who has been diagnosed with the syndrome, the likelihood that a second child will be born with the same abnormality is very high.

Happy Doll Syndrome and Canavan-Van Bogart-Bertrand Disease

Let's take a closer look at these diseases. You can recognize Engelman's syndrome somewhere from 3-7 years. Children have cramps, poor digestion, problems with coordination of movements. Most of them have strabismus and problems with the muscles of the face, because of which the smile is very often on the face. The movements of the child are very constrained. For doctors, this is understandable when a child tries to walk. Parents in most cases do not know what is happening and even more so with what it is connected. A little later, it is also noticeable that they cannot speak, they only try to mutter something inarticulately.

The reason why a child develops a syndrome is a problem in the 15th chromosome. The disease is extremely rare - 1 case per 15 thousand births.

Another disease - Canavan's disease - is characterized by the fact that the child has a weak muscle tone, he has problems with swallowing food. The disease is caused by damage to the central nervous system. The reason is the defeat of one gene on the 17th chromosome. As a result, the nerve cells of the brain are destroyed with progressive speed.

Signs of the disease can be seen at 3 months of age. Canavan disease manifests itself as follows:

1. Macrocephaly.
2. Seizures appear at the age of one month.
3. The child is unable to hold his head upright.
4. After 3 months, tendon reflexes increase.
5. Many children go blind by the age of 2.

As you can see, human hereditary diseases are very diverse. This list is for example only and is far from complete.

I would like to note that if both parents have a violation in 1 and the same gene, then the chances of giving birth to a sick child are high, but if there are anomalies in different genes, then there is no need to be afraid. It is known that in 60% of cases, chromosomal abnormalities in the fetus lead to miscarriage. But still 40% of such children are born and fight for their lives.

hereditary diseases pediatricians, neurologists, endocrinologists

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hereditary diseases- a large group of human diseases caused by pathological changes in the genetic apparatus. Currently, more than 6 thousand syndromes with a hereditary mechanism of transmission are known, and their overall frequency in the population ranges from 0.2 to 4%. Some genetic diseases have a certain ethnic and geographical prevalence, others are found with the same frequency throughout the world. The study of hereditary diseases is mainly within the competence of medical genetics, however, almost any medical specialist can encounter such a pathology: pediatricians, neurologists, endocrinologists, hematologists, therapists, etc.

Hereditary diseases should be distinguished from congenital and family pathology. Congenital diseases can be caused not only by genetic, but also by unfavorable exogenous factors affecting the developing fetus (chemical and medicinal compounds, ionizing radiation, intrauterine infections, etc.). However, not all hereditary diseases appear immediately after birth: for example, signs of Huntington's chorea usually first manifest themselves over the age of 40 years. The difference between hereditary and family pathology is that the latter may be associated not with genetic, but with social or professional determinants.

The occurrence of hereditary diseases is caused by mutations - sudden changes in the genetic properties of an individual, leading to the emergence of new, non-normal traits. If mutations affect individual chromosomes, changing their structure (due to loss, acquisition, variation in the position of individual sections) or their number, such diseases are classified as chromosomal. The most common chromosomal abnormalities are, duodenal ulcer, allergic pathology.

Hereditary diseases can manifest themselves both immediately after the birth of a child, and at different stages of life. Some of them have an unfavorable prognosis and lead to early death, others do not significantly affect the duration and even quality of life. The most severe forms of hereditary pathology of the fetus cause spontaneous abortion or are accompanied by stillbirth.

Thanks to advances in the development of medicine, about a thousand hereditary diseases today can be detected even before the birth of a child using prenatal diagnostic methods. The latter include ultrasound and biochemical screening of I (10-14 weeks) and II (16-20 weeks) trimesters, which are carried out for all pregnant women without exception. In addition, if there are additional indications, invasive procedures may be recommended: chorionic villus biopsy, amniocentesis, cordocentesis. With a reliable establishment of the fact of severe hereditary pathology, a woman is offered an artificial termination of pregnancy for medical reasons.

All newborns in the first days of their lives are also subject to examination for hereditary and congenital metabolic diseases (phenylketonuria, adrenogenital syndrome, congenital adrenal hyperplasia, galactosemia, cystic fibrosis). Other hereditary diseases that are not recognized before or immediately after the birth of a child can be detected using cytogenetic, molecular genetic, biochemical research methods.

Unfortunately, a complete cure for hereditary diseases is currently not possible. Meanwhile, in some forms of genetic pathology, a significant prolongation of life and the provision of its acceptable quality can be achieved. In the treatment of hereditary diseases, pathogenetic and symptomatic therapy is used. The pathogenetic approach to treatment involves replacement therapy (for example, with blood clotting factors in hemophilia), limiting the use of certain substrates in phenylketonuria, galactosemia, maple syrup disease, replenishing the deficiency of a missing enzyme or hormone, etc. Symptomatic therapy includes the use of a wide range of drugs, physiotherapy, rehabilitation courses (massage, exercise therapy). Many patients with genetic pathology from early childhood need correctional and developmental classes with a teacher-defectologist and speech therapist.

The possibilities of surgical treatment of hereditary diseases are reduced mainly to the elimination of severe malformations that impede the normal functioning of the body (for example, correction of congenital heart defects, cleft lip and palate, hypospadias, etc.). Gene therapy of hereditary diseases is still rather experimental in nature and is still far from being widely used in practical medicine.

The main direction in the prevention of hereditary diseases is medical genetic counseling. Experienced geneticists will consult a married couple, predict the risk of offspring with a hereditary pathology, and provide professional assistance in making a decision about childbearing.