Genetic research. Genetic predispositions Genetic examination of the syndrome

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Indications for examination, stages of treatment and where to find it in Moscow?

Geneticists are doctors whose competence includes identifying and preventing congenital and hereditary abnormalities caused by gene mutations. It is mandatory to contact geneticists when planning a pregnancy. If necessary, the geneticist will refer the patient for additional examinations or comprehensive genetic diagnostics.

The main task of a good geneticist is the timely identification and prediction of the risks of developing certain hereditary diseases in the fetus or in a born child. Genetic consultation is sometimes indicated for adult patients.

Who should be examined by a geneticist?

• — potential parents planning pregnancy;
• - women carrying a fetus (especially in the 1st trimester of pregnancy);
• - people with hereditary diseases.

What diseases can geneticists identify?

Geneticists can identify and prevent the development of such diseases:

• — monogenic diseases;
• - chromosomal abnormalities;
• - genetic reasons for failure to carry a pregnancy to term;
• - multifactorial conditions.

During the research process, the specialist will conduct DNA diagnostics, which will help identify genetic diseases before their manifestations begin, as well as identify possible hidden carrying of defective genes.

In what cases is it necessary to contact geneticists?

• - if the future parents have a blood connection;
• - if at the time of planning a future pregnancy the woman is over 35 years old or under 18 years old;
• - if a woman has had abortions or miscarriages in the past;
• - if a woman was diagnosed with an infectious disease during pregnancy;
• - if the expectant mother underwent x-rays during pregnancy, consumed alcohol, drugs, nicotine;
• - if previous children have developmental defects;
• - in cases where one or both parents work in an unsafe environment;
• - if one or both spouses have addictions to alcohol, smoking, or drugs;
• - if an ultrasound specialist diagnosed abnormalities in the fetus or pregnant woman.

Why is an examination with geneticists prescribed?

An appointment with a geneticist allows you to accomplish the following tasks:

• — establish the reasons for failure to carry a pregnancy to term;
• — identify genetic pathologies in the unborn child at the stage of intrauterine development;
• — identify the effect of taking medications on the fetus;
• — determine the potential risk of external factors affecting the health of the fetus.

The main stages of contacting a geneticist

1. Make an appointment with a specialist;
2. Conducting medical and genetic consultation of the patient;
3. Providing the patient with a genetic report with preventive recommendations, as well as referrals for genetic testing.

An examination by a geneticist goes something like this:

1. The geneticist collects the medical history of both partners;
2. The specialist prescribes molecular biological tests to patients;
3. The doctor issues a written medical report on the risks, according to the results of laboratory tests and theoretical calculations;
4. The patient receives advice on planning a child.

The knowledge and experience of geneticists allow not only to conduct high-quality diagnostics, but also to solve the problems of having children with developmental defects. So, if a couple has a high risk of having an unhealthy child, then it makes sense to use donor sperm, eggs, or the service surrogacy. However, even if both partners are completely healthy, consulting a geneticist will not hurt.

Where and how to find a good geneticist?

To find a qualified geneticist, you can use various sites for finding doctors (for example, DocDoc, sites of government clinics and other Internet resources). It should be noted that usually such sites have a large database of doctors who are ready to provide quick and comprehensive assistance. At the clinic, you can be examined by a doctor, as well as undergo laboratory and diagnostic examinations of the body on site.

We wish you and your future children good health!

Adrenogenital syndrome, CYP210HB 9 tsp.

Genetic testing for the presence of frequent mutations in the CYP21OHB gene is aimed at diagnosing adrenogenital syndrome, a disease caused by a genetic defect in the enzymatic systems that are involved in the synthesis of corticosteroids, and accompanied by abnormalities of sexual and somatic development, hyperandrogenism.

The occurrence of isolated malformations in the fetus

Identification of individual characteristics in the main genes of folate cycle enzymes to assess the likelihood of folic acid deficiency during pregnancy (it is recommended to evaluate it in combination with an immunochemical test to determine homocysteine ​​levels).

Typing of genes of the HLA class II system

Identification of individual characteristics at three loci of HLA class II genes to assess susceptibility to the development of certain autoimmune diseases, including during pregnancy.

Molecular genetic study of HLA-B27

HLA-B27 genotyping (HLA class I). Can be used in the differential diagnosis of seronegative spondyloarthropathies, including ankylosing spondylitis.

Identification of combinations of genotypes by loci of genes of the HLA class II system. May be recommended to assess the genetic risk of developing celiac disease.

Determination of the Rh factor genotype

The test includes a study of the RHD gene - the Rh factor gene with the determination of heterozygous or homozygous carriage of the Rh factor. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Determination of the Rh factor genotype (without a description of the results by a geneticist)

The test includes a study of the RHD gene - the Rh factor gene with the determination of heterozygous or homozygous carriage of the Rh factor. The geneticist will not provide a description of the results.

Extended study of genes of the hemostatic system (with a description of the results by a geneticist)

Extended study of genes of the hemostatic system (without description of the results by a geneticist)

Identification of individual characteristics in 12 genes of the hemostasis system. Extended profile. May be recommended to assess the risk of developing increased/decreased blood clotting.

Thrombosis: extended panel

Thrombosis: extended panel (without description of results by a geneticist)

Identification of individual characteristics in 6 genes of the hemostasis system to assess the presence of risk factors for the development of thrombosis and increased homocysteine ​​levels (genes for prothrombin, Leiden factor and enzymes of folate cycle reactions).

Thrombosis - minimum: shortened panel

Thrombosis - minimum: abbreviated panel (without description of the results by a geneticist)

Identification of changes in 2 main genes of the hemostatic system to assess the presence of risk factors for the development of thrombosis (prothrombin and Leiden factor genes).

Fibrinogen - gene

The analysis is aimed at studying polymorphisms in the fibrinogen β-polypeptide gene FGB, which may cause an increased risk of developing thrombophilic conditions. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Fibrinogen - gene (without a description of the results by a geneticist)

The analysis is aimed at studying polymorphisms in the fibrinogen β-polypeptide gene FGB, which may cause an increased risk of developing thrombophilic conditions. The geneticist will not provide a description of the results.

Hyperhomocysteinemia

Platelet hyperaggregation

The study of polymorphisms in the genes of integrin alpha-2 and platelet glycoprotein 1b is carried out to identify genetic predisposition to the early development of myocardial infarction, ischemic stroke, thromboembolism, as well as to assess the risk of developing thrombosis. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Platelet hyperaggregation (without a description of the results by a geneticist)

The study of polymorphisms in the genes of integrin alpha-2 and platelet glycoprotein 1b is carried out to identify genetic predisposition to the early development of myocardial infarction, ischemic stroke, thromboembolism, as well as to assess the risk of developing thrombosis. The geneticist will not provide a description of the results.

Platelet fibrinogen receptor

Determination of polymorphisms in the platelet fibrinogen receptor gene (β3-integrin) is performed to identify hereditary predisposition to thrombophilic conditions. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Platelet fibrinogen receptor (without description of results by a geneticist)

Determination of polymorphisms in the platelet fibrinogen receptor gene (β3-integrin) is performed to identify hereditary predisposition to thrombophilic conditions. The geneticist will not provide a description of the results.

Hyperhomocysteinemia (without description of the results by a geneticist)

Identification of changes in the main genes of folate cycle enzymes to assess the presence of a tendency to hyperhomocysteinemia (it is recommended to evaluate in combination with an immunochemical test to determine homocysteine ​​levels).

Cardiovascular diseases

During the study, genetic risk factors for the development of arterial hypertension, atherosclerosis, coronary heart disease, myocardial infarction, and ischemic stroke are identified.

Arterial hypertension (full panel)

Analysis of polymorphisms in the ACE, AGT, NOS3 genes makes it possible to detect hereditary risk factors for the development of arterial hypertension. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Arterial hypertension (full panel) (without description of the results by a geneticist)

Analysis of polymorphisms in the ACE, AGT, NOS3 genes makes it possible to detect hereditary risk factors for the development of arterial hypertension. The geneticist will not provide a description of the results.

Arterial hypertension associated with disturbances in the renin-angiotensin system

The test allows you to determine the presence of genetic risk factors for the development of arterial hypertension as a result of narrowing of the lumen of blood vessels and disturbances in water-salt balance that occur in the presence of polymorphisms in the ACE and AGT genes. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Arterial hypertension associated with disorders in the reninangiotensin system (without a description of the results by a geneticist)

The test allows you to determine the presence of genetic risk factors for the development of arterial hypertension as a result of narrowing of the lumen of blood vessels and disturbances in water-salt balance that occur in the presence of polymorphisms in the ACE and AGT genes. The geneticist will not provide a description of the results.

Arterial hypertension associated with disturbances in the functioning of endothelial NO synthase

As a result of the analysis of polymorphisms in the NO synthase gene, it is possible to assess the genetic risk of developing arterial hypertension as a result of impaired vascular wall tone. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Arterial hypertension associated with disturbances in the functioning of endothelial NO synthase (without a description of the results by a geneticist)

As a result of the analysis of polymorphisms in the NO synthase gene, it is possible to assess the genetic risk of developing arterial hypertension as a result of impaired vascular wall tone. The geneticist will not provide a description of the results.

IHD, myocardial infarction

The study makes it possible to identify hereditary risk factors for the development of thrombosis, arterial hypertension and atherosclerosis by analyzing polymorphisms in the ACE, AGT, ApoE, NOS3, ITGB3, ITGA2 genes. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

IHD, myocardial infarction (without description of the results by a geneticist)

The study makes it possible to identify hereditary risk factors for the development of thrombosis, arterial hypertension and atherosclerosis by analyzing polymorphisms in the ACE, AGT, ApoE, NOS3, ITGB3, ITGA2 genes. The geneticist will not provide a description of the results.

Ischemic stroke (without description of the results by a geneticist)

Ischemic stroke

Genetic risk factors for thrombosis and ischemic stroke. Analysis of the presence of polymorphisms in the genes of platelet glycoproteins and fibrinogen.

Crohn's disease

The test is used in the diagnosis of Crohn's disease, to determine the prognosis of the severity of the disease and the risk of complications. The study is also used for the differential diagnosis of Crohn's disease with ulcerative colitis and as a prognostic test in relatives of patients with Crohn's disease.

Cancers associated with environmental toxins

The study includes the identification of hereditary risk factors for the development of cancer under the influence of toxic load by analyzing the presence of polymorphisms in the genes of the detoxification system.

Marker for the development of Ph'-negative chronic myeloproliferative diseases (CMPD): quantitative determination of the ratio of normal and mutant alleles 617V/617F of the JAK2 gene.

Study of the Janus kinase gene. It may be recommended before starting treatment for CMPD and to determine the effectiveness of the therapy.

Hereditary cases of BRCA-associated cancer in men (breast, pancreatic, prostate, testicular cancer), 2 genes: BRCA1, BRCA2 (without describing the results)

Hereditary cases of BRCA-associated cancer in men (breast, pancreatic, prostate, testicular cancer), 2 genes: BRCA1, BRCA2

Determination of the 8 most common mutations in the BRCA1, BRCA2 (Breast Cancer 1/2) genes associated with the development of BRCA-associated cancer in men.

Multiple endocrine neoplasia syndrome type 2B

Multiple endocrine neoplasia syndrome type 2B belongs to a group of familial tumor syndromes associated with specific mutations of the RET proto-oncogene, which are identified during the study.

Gilbert's syndrome, UGT1A1

Genetic diagnosis of Gilbert's syndrome - unconjugated benign hyperbilirubinemia - is based on the study of possible mutations in the promoter region of the UGT1A1 gene.

Osteoporosis: complete panel

Osteoporosis: full panel (without description of results by a geneticist)

Genetic risk factors for osteoporosis. Analysis of the presence of polymorphisms in the alpha-1 chain genes of type 1 collagen protein and calcitonin receptor.

Osteoporosis: abbreviated panel

Genetic risk factors for osteoporosis. Analysis of the presence of polymorphisms in the alpha-1 chain genes of type 1 collagen protein and calcitonin receptor.

Osteoporosis: shortened panel (without description of results by a geneticist)

Genetic risk factors for osteoporosis. Analysis of the presence of polymorphisms in the genes of the alpha-1 chain of type 1 collagen protein and the calcitonin receptor.

Osteoporosis: vitamin D receptor

The study of genetic risk factors for the development of osteoporosis is carried out in case of a family history of diseases of the bone system, as well as in the presence of disorders of mineral metabolism. The result form displays information about polymorphisms obtained during molecular genetic research, with comments.

Osteoporosis: vitamin D receptor (without description of results by a geneticist)

The study of genetic risk factors for the development of osteoporosis is carried out in case of a family history of diseases of the bone system, as well as in the presence of disorders of mineral metabolism. The geneticist will not provide a description of the results.

Folic acid metabolism

Folic acid metabolism (without a description of the results by a geneticist)

Identification of individual characteristics in the main genes of folate cycle enzymes to assess the presence of a tendency to hyperhomocysteinemia (it is recommended to evaluate in combination with an immunochemical test to determine homocysteine ​​levels).

Hereditary hemochromatosis, type I. HFE

Identification of the 2 most common mutations in the HFE gene to assess the risk of developing type 1 hemochromatosis. Recommended when detecting an increase in ferritin concentration and % saturation of transferrin with iron in the blood serum.

Description of the results of the genetic test of the 2nd category of complexity (No. 118GP/BZ, 121GP/BZ, 123GP/BZ, 131GP/BZ, 141GP/BZ, 149GP/BZ, 150GP/BZ, 115GP/BZ, 152GP/BZ, 124GP/BZ, 154GP/BZ)

The study includes a description by a geneticist of the results of genetic tests, which fall into the second category of complexity.

Description of the results of the genetic test of the 3rd category of complexity (No. 122GP/BZ, 129GP/BZ, 120GP/BZ, 137GP/BZ, 138GP/BZ, 153GP/BZ, 151GP/BZ, 110GP/BZ, 114GP/BZ, 140GP/BZ, 7661БЗ, 7258БЗ, 134ГП/БЗ, 135ГП/БЗ, 136ГП/БЗ)

The study includes a description by a geneticist of the results of genetic tests, which fall into the third category of complexity.

Description of the results of the genetic test of the 4th category of complexity (No. 144GP/BZ, 143GP/BZ, 139GP/BZ, 145GP/BZ, 108GP/BZ, 19GP/BZ)

The study includes a description by a geneticist of the results of genetic tests, which fall into the fourth category of complexity.

Hydralazine and procainamide

The test includes an analysis of polymorphisms in the NAT-2 gene, which indicates the presence of hereditary factors for an increased risk of developing lupus-like syndrome and hepatotoxicity when taking cardiotropic drugs.

Isoniazid

The test includes an analysis of polymorphisms in the NAT-2 gene, which indicates the presence of hereditary factors for an increased risk of developing polyneuritis when taking isoniazid, associated with impaired metabolism.

ACE inhibitors, fluvastatin, ATII receptor blockers

Analysis of polymorphisms in the ACE gene is necessary to predict the nephroprotective effect of angiotensin-converting enzyme (ACE) inhibitors, a physiological regulator of blood pressure and water-salt metabolism in non-diabetic diseases. Through the study, it is possible to determine genetic markers of the effectiveness of atenolol in arterial hypertension with left ventricular hypertrophy or fluvastatin in coronary heart disease.

Metabolism of irinotecan, UGT1A1

A study of the promoter region of the uridine diphosphate glucuronidase 1 gene with analysis of polymorphisms in the UGT gene is used to determine the presence of a hereditary predisposition to an increased risk of developing adverse reactions when taking the anticancer drug irinotecan associated with impaired metabolism.

Penicillamine

Penicillamine is a drug from the group of detoxifying agents. Some variants of polymorphisms in the genes of the xenobiotic and carcinogen detoxification system are associated with increased clinical effectiveness of this drug. The study is aimed at identifying genetic markers that potentiate the clinical effectiveness of penicillamine use.

Statins

Polymorphisms in the apolipoprotein E (ApoE) gene are a genetic marker for decreased or increased clinical effectiveness with statin use. This study can be used when selecting a diet, deciding on the advisability of prescribing statins, lipid metabolism disorders, and also to determine the risk of cardiovascular diseases.

Beta blockers. CYP2D6 gene. Pharmacogenetics.

Cytochrome CYP2D6 is involved in the metabolism of drugs (β-blockers, antiarrhythmics, analeptics, antidepressants and narcotic analgesics) used in the treatment of a number of cardiovascular diseases and mental disorders. The study of polymorphisms in the CYP2D6 gene allows us to identify people with reduced CYP2D6 activity, since such patients need to individually select lower doses of drugs.

Aspirin and Plavix

During the study, polymorphisms in the ITGB3 gene, which is a genetic marker of resistance to antiplatelet therapy, are analyzed. The test results can be used to predict the effectiveness of antiplatelet therapy with aspirin and Plavix.

Uridine diphosphate glucuronidase, UGT1A1

A study of the promoter region of the uridine diphosphate glucuronidase 1 gene is carried out in the presence of clinical and/or laboratory signs of Gilbert's syndrome, when planning treatment with drugs that have hepatotoxic properties, as well as to determine the degree of risk of complications during irinotecan therapy.

Cytochrome CYP2C9

Analysis of the presence of polymorphisms in the cytochrome P450 gene is carried out to identify hereditary factors for impaired detoxification. CYP2C9 is involved in drug metabolism. When the activity of cytochrome CYP2C9 decreases, the metabolism of drugs slows down, resulting in an increase in their concentration in the blood, which may cause the development of undesirable reactions.

Rh factor of the fetus. Detection of the RHD gene of the fetus in the mother's blood

Determining the Rh status of the fetus from the mother's blood is used to select tactics for managing an Rh-negative pregnant woman. In a genotypically Rh-positive mother, obtaining a result is impossible.

From parents, a child can acquire not only a certain eye color, height or face shape, but also inherited ones. What are they? How can you detect them? What classification exists?

Mechanisms of heredity

Before talking about diseases, it is worth understanding what they are. All information about us is contained in the DNA molecule, which consists of an unimaginably long chain of amino acids. The alternation of these amino acids is unique.

The fragments of a chain of DNA are called genes. Each gene contains complete information about one or more characteristics of the body, which is transmitted from parents to children, for example, skin color, hair, character trait, etc. When they are damaged or their work is disrupted, genetic diseases that are inherited occur.

DNA is organized into 46 chromosomes or 23 pairs, one of which is the sex chromosome. Chromosomes are responsible for gene activity, copying, and recovery from damage. As a result of fertilization, each couple has one chromosome from the father and another from the mother.

In this case, one of the genes will be dominant, and the other will be recessive or suppressed. To put it simply, if the father’s gene responsible for eye color turns out to be dominant, then the child will inherit this trait from him, and not from the mother.

Genetic diseases

Inherited diseases occur when disturbances or mutations occur in the mechanism for storing and transmitting genetic information. An organism whose gene is damaged will pass it on to its descendants in the same way as healthy material.

In the case when the pathological gene is recessive, it may not appear in the next generations, but they will be its carriers. The chance that it will not manifest itself exists when a healthy gene also turns out to be dominant.

Currently, more than 6 thousand hereditary diseases are known. Many of them appear after 35 years, and some may never make themselves known to the owner. Diabetes mellitus, obesity, psoriasis, Alzheimer's disease, schizophrenia and other disorders occur with extremely high frequency.

Classification

Genetic diseases transmitted by inheritance have a huge number of varieties. To divide them into separate groups, the location of the disorder, causes, clinical picture, and nature of heredity can be taken into account.

Diseases can be classified according to the type of inheritance and location of the defective gene. So, it is important whether the gene is located on the sex or non-sex chromosome (autosome), and whether it is suppressive or not. Diseases are distinguished:

• Autosomal dominant - brachydactyly, arachnodactyly, ectopia lentis.
• Autosomal recessive - albinism, muscular dystonia, dystrophy.
• Limited by gender (observed only in women or men) - hemophilia A and B, color blindness, paralysis, phosphate diabetes.

The quantitative-qualitative classification of hereditary diseases distinguishes genetic, chromosomal and mitochondrial types. The latter refers to DNA disorders in mitochondria outside the nucleus. The first two occur in DNA, which is found in the cell nucleus, and have several subtypes:

Monogenic	Mutations or absence of a gene in nuclear DNA.	Marfan syndrome, adrenogenital syndrome in newborns, neurofibromatosis, hemophilia A, Duchenne myopathy.
Polygenic	Predisposition and action	Psoriasis, schizophrenia, coronary disease, cirrhosis, bronchial asthma, diabetes mellitus.
Chromosomal
	Changes in chromosome structure.	Miller-Dicker, Williams, Langer-Gidion syndromes.
	Change in the number of chromosomes.	Down's, Patau's, Edwards', Klifenter's syndromes.

Causes

Our genes tend not only to accumulate information, but also to change it, acquiring new qualities. This is a mutation. It occurs quite rarely, approximately 1 time in a million cases, and is transmitted to descendants if it occurs in germ cells. For individual genes, the mutation frequency is 1:108.

Mutations are a natural process and form the basis of evolutionary variability in all living beings. They can be useful and harmful. Some help us better adapt to our environment and way of life (for example, opposable thumb), others lead to diseases.

The occurrence of pathologies in genes is increased by physical, chemical and biological factors. Some alkaloids, nitrates, nitrites, some food additives, pesticides, solvents and petroleum products have this property.

Among the physical factors are ionizing and radioactive radiation, ultraviolet rays, excessively high and low temperatures. Rubella viruses, measles, antigens, etc. act as biological causes.

Genetic predisposition

Parents influence us not only through upbringing. It is known that some people are more likely to develop certain diseases than others due to heredity. Genetic predisposition to diseases occurs when one of the relatives has abnormalities in the genes.

The risk of a particular disease in a child depends on his gender, because some diseases are transmitted only through one line. It also depends on the person's race and the degree of relationship with the patient.

If a person with the mutation gives birth to a child, then the chance of inheriting the disease will be 50%. The gene may well not manifest itself in any way, being recessive, and in the case of marriage with a healthy person, its chances of being passed on to descendants will be already 25%. However, if the spouse also has such a recessive gene, the chances of its manifestation in the descendants will again increase to 50%.

How to identify the disease?

The genetic center will help to detect the disease or predisposition to it in time. Usually there is one in all major cities. Before taking the tests, a consultation is held with a doctor to find out what health problems are observed in relatives.

A medical genetic examination is carried out by taking blood for analysis. The sample is carefully examined in the laboratory for any abnormalities. Expectant parents usually attend such consultations after pregnancy. However, it is worth coming to the genetic center during its planning.

Hereditary diseases seriously affect the mental and physical health of the child and affect life expectancy. Most of them are difficult to treat, and their manifestation can only be corrected by medical means. Therefore, it is better to prepare for this even before conceiving a baby.

Down syndrome

One of the most common genetic diseases is Down syndrome. It occurs in 13 cases out of 10,000. This is an anomaly in which a person has not 46, but 47 chromosomes. The syndrome can be diagnosed immediately at birth.

The main symptoms include a flattened face, raised corners of the eyes, a short neck and lack of muscle tone. The ears are usually small, the eyes are oblique, and the shape of the skull is irregular.

Sick children experience concomitant disorders and diseases - pneumonia, ARVI, etc. Exacerbations may occur, for example, loss of hearing, vision, hypothyroidism, heart disease. With downism it is slowed down and often remains at the level of seven years.

Constant work, special exercises and medications significantly improve the situation. There are many cases where people with a similar syndrome were quite able to lead an independent life, find work and achieve professional success.

Hemophilia

A rare hereditary disease that affects men. Occurs once in 10,000 cases. Hemophilia has no cure and occurs as a result of a change in one gene on the sex X chromosome. Women are only carriers of the disease.

The main characteristic is the absence of a protein that is responsible for blood clotting. In this case, even a minor injury causes bleeding that is not easy to stop. Sometimes it manifests itself only the next day after the injury.

Queen Victoria of England was a carrier of hemophilia. She passed the disease on to many of her descendants, including Tsarevich Alexei, the son of Tsar Nicholas II. Thanks to her, the disease began to be called “royal” or “Victorian”.

Angelman syndrome

The disease is often called “happy doll syndrome” or “Parsley syndrome”, as patients experience frequent outbursts of laughter and smiling, and chaotic hand movements. This anomaly is characterized by disturbances in sleep and mental development.

The syndrome occurs once in 10,000 cases due to the absence of certain genes on the long arm of chromosome 15. Angelman disease develops only if genes are missing from the chromosome inherited from the mother. When the same genes are missing from the paternal chromosome, Prader-Willi syndrome occurs.

The disease cannot be completely cured, but it is possible to alleviate the symptoms. For this purpose, physical procedures and massages are performed. Patients do not become completely independent, but during treatment they can take care of themselves.

In vitro fertilization results in a successful pregnancy only in 40-45% of cases. Therefore, it is necessary to reduce the risk of having a child with congenital anomalies so that the long-awaited pregnancy is not overshadowed by intrauterine pathology of the fetus that is incompatible with life. For this purpose, preimplantation genetic diagnosis has been developed. This is the determination of genetic diseases in the embryo before transfer to the uterus.

How are genetic diseases inherited?

Not every mutation or defective trait in parents can cause manifestations of the disease in a child. It all depends on whether a dominant or recessive trait is inherited from each spouse, and what combination of genes the child will get.

If a child is passed on a gene that is dominant over a similar unchanged one, then there is a 50% risk that a hereditary pathology will manifest itself. Parents who have a recessive gene for the disease are carriers of the diseased genetic trait. For a child to develop clinical symptoms of pathology, he must inherit two recessive genes.

There are also gender-linked diseases. In women, the twenty-third pair of chromosomes is XX, in men it is XY. If one of the chromosomes in a woman’s genetic material is defective, then the development of the disease is blocked by the second, but the pathological gene is carried. In men, the Y chromosome is not able to block the effects of the pathological X chromosome, so the disease manifests itself in the sons of such a couple, and 50% of daughters are carriers of the altered gene.

Preimplantation genetic diagnosis of embryos helps to establish with 100% accuracy in what combination the genetic material was inherited, whether the child will manifest a disease, or whether he will be a carrier of pathological symptoms.

Who needs genetic testing?

There are certain indications for PGD. It is recommended to carry out the study for women wishing to give birth after 34 years of age. At this age, even with natural pregnancy, the risks of having a child with genetic abnormalities increase.

Eggs gradually age and are exposed to various negative factors throughout life:

• bad habits of the mother (smoking, drinking alcohol);
• chronic diseases;
• treatment with medications;
• harmful working conditions (chemical reagents, physical factors in the form of high temperatures, vibration, ionizing radiation, electromagnetic fields);
• bad ecology.

With age, defective eggs accumulate and the risk of passing pathological genes to offspring increases. If such an embryo is transferred to the uterus, then in most cases it will not take root, and the pregnancy will be terminated by a miscarriage. Or, as the pregnancy progresses, a subsequent examination will reveal a pathology that will become an indication for termination. Preimplantation diagnosis helps to avoid psychological trauma associated with miscarriage or the birth of a defective child. A man falls into the risk age group over the age of 39 years. This also includes spouses with pathology of spermatogenesis.

It is necessary to examine couples who have autosomal dominant pathologies. 50% of their children will be carriers of the gene or have clinical signs of the disease.

Research is also carried out for:

• 2 or more unsuccessful attempts;
• 3 or more attempts to transfer high-quality embryos in women under 35 years of age, which did not result in pregnancy;
• risk group for late-onset diseases;
• desire to have an HLA-matched child in order to obtain stem cells to treat another child with a serious disease;
• the birth of a child compatible with the Rh factor to prevent conflict.

When carried out according to indications, PGD helps to avoid subsequent prenatal diagnosis, which reduces the risk of miscarriage.

Objectives of the study

Based on the indications for diagnostics, its goals can be determined:

1. Exclusion of embryos with an abnormal karyotype.
2. Establishing the reasons for the failure of previous IVF.
3. Reducing the risk of having a child with anomalies from carrier parents.
4. Identification of embryos with a predisposition to severe diseases.
5. The birth of a child who matches the HLA system for treatment of a brother or sister.
6. Reducing the risk of hemolytic disease when a child is born with a certain Rh factor.

Preimplantation genetic diagnosis of monogenic diseases is carried out to identify:

• cystic fibrosis;
• Tay-Sachs disease;
• hemophilia A;
• Duchenne muscular dystrophy;
• sickle cell anemia.

The search for chromosomal abnormalities includes the study of nine of them, which are the cause of the following syndromes:

• Down (trisomy 21 chromosomes);
• Patau (chromosome 13);
• Edwards (18);
• Klinefelter;
• “cat pupils” (22);
• chromosomes 15, 16, 17.

Genetic testing can also help identify many other diseases.

Diagnostic methods

Embryos or eggs are used for PGD. But in the first case, the study is more informative, because the embryo contains genetic material from the father, which can pass on defective genes.

During the study, a biopsy of one blastomere is performed in an embryo out of 4-10 available, which is at the stage of cleavage. This happens within 3-5 days. No harm is done to the unborn fetus.

The technique can only be used in an IVF procedure combined with artificial insemination with sperm. This is done so that during the blastomere biopsy the genetic material of the sperm that was not involved in fertilization is not taken for research.

Further and management of pregnancy proceeds as with conventional IVF. Only 2 days are allotted for analysis; replanting should occur no later than the 5th day of development. Wider possibilities for diagnostics in a cycle with cryopreservation. If you biopsy some embryos and then preserve them, you can safely perform as many studies as possible, and transfer a high-quality embryo for the next cycle.

Several methods for performing PGD have been developed.

• FISH method

Used to diagnose numerical or structural chromosomal changes - aneuploidies and translocations. The cell obtained from the biopsy is fixed on a glass slide, heated and cooled. In this case, its shell ruptures and the cytoplasm comes out. Sections of DNA are marked with fluorescent probes - special dyes. Then, using a special fluorescent microscope, specific chromosomes can be counted and normal and pathological ones can be identified.

The polymerase chain reaction is based on identifying specific copies of DNA. First, it is denatured in order to unwind the double strand and obtain a single fragment. By adding special enzymes, the amount of genetic material is gradually doubled. This makes it possible to detect defective sites in the nucleotide. The technique is used to search for monogenic diseases, when one or two spouses are identified as carriers of defective genes or with clinical signs of the disease.

• The latest NGS technique

An innovation is preimplantation genetic diagnostics in the cryocycle using the NGS method, with the help of which it becomes possible to study all 23 pairs of chromosomes. Its accuracy reaches 99.9%. At the same time, a study of monogenic and chromosomal pathologies, as well as mutations, is carried out. The technique allows one to distinguish balanced translocations from a normal set of chromosomes. Therefore, there is no need to repeat the blastomere biopsy. High automation of the process eliminates additional errors.

Benefits and Risks

The use of genetic analysis of the embryo at the cleavage stage increases the chances of successful implantation. It has been proven that chromosomal changes in embryos increase the likelihood of a non-developing pregnancy. In 21% of cases of spontaneous termination of pregnancy, including those obtained by IVF, the cause of termination is chromosomal pathology of the fetus. With age, the number of anomalies increases exponentially. If we consider that assisted reproductive technologies are most often used by women in the older age category, then the need for diagnostics before embryo transfer becomes clear.

The information obtained can be used by the doctor in further attempts at IVF, and will also suggest the reasons for previous unsuccessful attempts at fertilization.

When using PCR or fluorescent methods, only a certain number of chromosomes can be examined. Therefore, some defects may be inherited.

It happens that during preimplantation genetic diagnosis, an abnormal embryo is determined to be normal. In this case, subsequent prenatal diagnosis will help accurately diagnose the pathology. At this stage of scientific development, PGD is not able to completely replace the latter. Sometimes genetic abnormalities occur in a mosaic pattern. In this case, a biopsy of one blastomere will confirm the normal state of the embryo, and the disease will arise due to the fault of the altered cell.

Damage to the embryo during biopsy occurs extremely rarely, in 0.1% of cases. It should also be remembered that even after successful diagnosis and transfer of a normal embryo, IVF may fail for unknown reasons. In this case, the cause may be immune disorders in the mother’s body or undiagnosed diseases. Only a complete examination in preparation for IVF and a healthy lifestyle increase the chances of pregnancy.

When planning a pregnancy, genetic testing plays a very important role, as it makes it possible to minimize the likelihood of having a baby with any pathologies. Unfortunately, most embryos die in the early stages precisely because of various anomalies and genetic failures. What this examination consists of, you will find out below.

Who needs to visit a geneticist?

For some couples, consultation with a geneticist during preparation for conception is mandatory:

• if any of the parents in the family had genetic diseases,
• husband and wife are related to each other,
• previous pregnancies ended in stillbirth, miscarriages, there was a frozen pregnancy,
• the couple has children with developmental defects,
• age: woman less than 16 or more than 35 years old, man more than 40 years old,
• at least one of the parents was in contact with radiation, chemicals that can negatively affect the conception and development of the baby,
• one of the spouses took medications that are incompatible with pregnancy,
• a couple has been unable to conceive a baby for 12 months or more.

Important: one of the main reasons for miscarriage is genetic incompatibility between husband and wife. This happens if the HLA (this is a human leukocyte antigen) of a man largely coincides with the HLA of a woman. As a result of this combination, the woman’s body perceives the embryo as a foreign body, rejecting it.

The main task of genetic research when planning a pregnancy to determine the compatibility of spouses is to identify discrepancies in the chromosomes of future parents. And the more discrepancies, the higher the chance of carrying and giving birth to a healthy baby.

What does a consultation involve when planning a pregnancy?

Even a healthy person can be a carrier of damaged genes

At the appointment, the geneticist will conduct a thorough survey of the couple about past illnesses, lifestyle, chronic illnesses, as well as the health of the husband and wife’s relatives. The specialist needs all this information in order to prescribe an examination for future parents. As a result of the tests, the geneticist individually makes a genetic prognosis for the child’s development, and also determines the risk of developing diseases and gives recommendations for pregnancy planning.

If a married couple is at risk, they need to undergo cytological examination(in order to determine the quantity and quality of chromosomes), a man needs to undergo a test (to exclude possible pathologies in sperm), he also needs to undergo HLA - typing(to determine the compatibility of spouses).

There are 3 levels of risk, which are determined based on the results of a genetic study:

• low (up to 10%) – the couple will have a healthy baby,
• average (10-20%) – the possibility of some pathologies of fetal development is not excluded. Therefore, the woman will need to be observed during pregnancy,
• high - in this case it is better to refrain from pregnancy, since there is a high probability of having a baby with serious pathologies (but you can use it).

What is the essence of cytogenetic analysis?

Cytogenetic analysis is a blood test of spouses, which makes it possible to:

• Conduct an analysis of the chromosome set of a man and a woman.

Even an absolutely healthy person can be a carrier of some chromosomal rearrangements and not be aware of it. This will not affect his health in any way, but it may not have the best effect on the child’s development.

• Assess the degree of risk for future pregnancies, taking into account past complications (miscarriages, missed abortions, birth of children with developmental anomalies).
• Prescribe and explain the need for prenatal diagnostics in future pregnancies.

This type of diagnosis involves conducting tests during the process of bearing a child. It allows you to clarify the condition of the fetus, as well as determine its chromosome set.

Interesting: Chromosomes can only be seen under a microscope at certain stages of cell division. Therefore, in order to study the chromosome set of future parents, blood is taken from them, from which lymphocytes are isolated. Next, the cells are stimulated to begin dividing and at a certain stage they are treated with a special solution that stops division precisely at the stage when chromosomes are visible.

A special dye is then used to give each individual chromosome a specific shape. A geneticist studies 11-13 chromosomes to identify changes in the karyotype (set of chromosomes).

Genetic testing methods

After the woman is registered, the gynecologist conducts a thorough interview and studies the patient’s outpatient card in order to have an idea of ​​the possible risks for the development of the fetus.

Sometimes even at such early stages a pregnant woman is referred for consultation with a geneticist. The period at which a pregnant woman needs to see a geneticist depends on the indications:

All genetic testing methods are divided into 2 groups: invasive and non-invasive.

Non-invasive methods

The first ultrasound examination is carried out at 11-12 weeks. During this period, it is already possible to identify some fetal malformations. This may be indicated by thickening of the fetal nuchal region (often a sign of Down syndrome).

Women with similar ultrasound results are referred for additional studies, which make it possible to obtain a sample of cells from the placenta in order to reliably determine the chromosome composition of the fetus.

The second ultrasound examination is carried out at 20-22 weeks. During this period, deviations in the development of the face, arms and legs, as well as internal systems and organs of the fetus can be identified.

Ultrasound at 30-32 weeks allows you to assess the condition of the circulatory system, as well as determine delays in fetal development.

This is how amniocentesis is performed.

1. Biochemical blood test (screening)

The embryonic tissues of the fetus produce special proteins: protein (PAPP), human chorionic gonadotropin (hCG), alphafetoprotein (AFP). By changes in the concentration of these substances in the blood of a pregnant woman, various pathologies of fetal development can be determined.

Such studies are carried out within a certain time frame. The level of PAPP and hCG is determined at 10-13 weeks. AFP level – at 16-20 weeks. If the test results are outside the normal range, the woman is referred to a geneticist.

Invasive diagnostic methods

These studies are carried out exclusively for compelling medical reasons, as they can harm the health of the woman and child. Invasive diagnostics involves taking material (umbilical cord blood, placental cells, amniotic fluid) from the uterus to determine the karyotype of the fetus and exclude or confirm diagnoses with developmental delay.

These studies are carried out in a hospital under ultrasound guidance. After the tests, the woman remains under the supervision of specialists for another 3 hours. Sometimes certain medications are prescribed to a pregnant woman to prevent complications. Diagnostic methods have been developed to identify 300 of the 5,000 existing hereditary diseases.

TO invasive research includes:

1. Chorionic villus biopsy

This is the collection of cells from the placenta. It is carried out for a period of 9-12 weeks. The material is collected through the woman’s abdominal wall. Results are obtained 3-4 days after the study. The risk of miscarriage after chorionic villus sampling is about 2%. This method has the advantages: early implementation, quick results, which makes it possible to identify serious pathologies of fetal development and terminate pregnancy in the early stages.

1. Amniocentesis

This is a collection of amniotic fluid at 16-24 weeks. This invasive method is the safest, since the risk of miscarriage after amniocentesis is only 1%. But there are also some disadvantages: the cells obtained after collection are not enough for analysis. They need to reproduce, and for this they need to spend a lot of time - about 2-6 weeks.

1. Cordocentesis

Cord blood analysis is a highly informative method that takes about 5 days to obtain results. It is carried out at 22-25 weeks.

1. Placentocentesis

This analysis involves collecting placental cells for research. It is carried out for a period of 12-22 weeks. The risk of complications after the analysis is 3-4%.

All of the above examination methods are carried out under anesthesia and under strict ultrasound control.

Genotype of father and mother when planning pregnancy

There are two main concepts in genetics: phenotype and genotype. A genotype is a set of genes. Phenotype is the external manifestations of a specific trait, which depends on both the genotype and external factors.

Ultrasound at 9-11 weeks reveals abnormalities in fetal development

A person has about 35 thousand genes, which are unique, just like fingerprints. The study of the genotype makes it possible to find out the genetic characteristics of a person, his heredity, compatibility with another person, and predisposition to many diseases.

People with the same blood type can have completely different sets of genes.

Interestingly, there are several surprising patterns:

• if mom and dad have the first blood group, the baby will only have the first group,
• if mom or dad has type 1, the child cannot have blood type 4,
• If at least one of the parents has a fourth blood group, the baby cannot have a second.

Prevention of genetic abnormalities of the fetus

In recent years, when planning pregnancy, periconceptional prophylaxis has been widely practiced, which makes it possible to significantly reduce the likelihood of having a baby with any congenital developmental anomalies. Periconceptional prophylaxis assumes:

1. Examination of future parents before conception, which makes it possible to identify and treat various diseases. Infections, hormonal imbalances, and disturbances in the functioning of the endocrine system can adversely affect conception and the formation of organs and systems of the fetus.
2. Taking multivitamin complexes 2-3 months before the expected conception. The preparations must contain: B vitamins, folic acid, ascorbic acid, vitamin A.
3. Genetic testing when planning pregnancy allows you to identify various pathologies of fetal development in the early stages.

4. Closely related marriages are extremely undesirable: the closer the relationship between husband and wife, the higher the risk of having a child with serious developmental anomalies.