Everyone has it healthy person there are 6-8 damaged genes, but they do not disrupt cell functions and do not lead to disease, since they are recessive (non-manifest). If a person inherits two similar abnormal genes from his mother and father, he becomes ill. The probability of such a coincidence is extremely low, but it increases sharply if the parents are relatives (that is, they have a similar genotype). For this reason, the incidence 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 impaired cell function and developmental defects.
A doctor can determine the risk of a possible genetic anomaly by asking you about diseases of relatives “up to the third generation” on both your side and your husband’s side.
There are a great many genetic diseases, some of which 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 impairment physical development. The disease occurs due to the presence of the third chromosome in the 21st pair (in total, a person has 23 pairs of chromosomes). It is the most common genetic disorder, affecting approximately one in 700 births. The incidence of Down syndrome increases in children born by women over 35 years old. 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 condition are usually very vertically challenged and their ovaries do not function.
X trisomy syndrome- a disease in which a girl is born with three X chromosomes. This disease occurs on average in one in 1000 girls. Trisomy X syndrome is characterized by a slight delay mental development and in some cases, infertility.
Klinefelter syndrome- a disease in which a boy has one extra chromosome. The disease occurs in one boy out of 700. Patients with Klinefelter syndrome usually have high growth, there are no noticeable external developmental anomalies (after puberty, the growth of facial hair is difficult and the mammary glands are somewhat enlarged). The intelligence of patients is usually normal, but speech impairments are common. Men suffering from Klinefelter syndrome are usually infertile.
Cystic fibrosis- a genetic disease in which the functions of many glands are disrupted. Cystic fibrosis affects only Caucasian people. About one in 20 white people has one damaged gene that, if manifested, can cause cystic fibrosis. The disease occurs if a person receives two such 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. Dehydration occurs and the viscosity of the gland secretion increases. As a result, a thick secretion blocks their activity. In patients with cystic fibrosis, protein and fat are poorly absorbed, and as a result, growth and weight gain are greatly reduced. Modern treatment methods (taking enzymes, vitamins and a special diet) allow half of 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 clotting factors. The disease is inherited through the female line, and affects the vast majority of boys (on average, one in 8,500). 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. People with hemophilia should not take medications that reduce blood clotting (for example, aspirin, heparin, and some pain relievers). To prevent or stop bleeding, the patient is administered a plasma concentrate containing a large number of missing clotting factor.
Tay Sachs disease- a genetic disease characterized by the accumulation of phytanic acid (a product of fat breakdown) in tissues. The disease occurs mainly among Ashkenazi Jews and French Canadians (one in 3,600 newborns). Children with Tay-Sachs disease early age are delayed in development, then paralysis and blindness occur. As a rule, patients live up to 3-4 years. Treatment methods of this disease does not exist.
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Books
- Childhood diseases, Belopolsky Yuri Arkadevich. The health of a child of any age is a special task for a doctor, because a growing organism requires more attention and greater vigilance in relation to diseases. Scheduled medical examinations, identification...
- Introduction to molecular diagnostics and gene therapy of hereditary diseases, V. N. Gorbunova, V. S. Baranov. The book outlines modern ideas about the structure of the human genome, methods for studying it, studying genes whose mutations lead to severe hereditary pathology: considered...
Content
During his life, a person suffers from many mild or severe diseases, but in some cases he is born with them. Hereditary diseases or genetic disorders appear in a child due to a mutation in one of the DNA chromosomes, which leads to the development of the disease. Some of them carry only external changes, but there are a number of pathologies that threaten the baby’s life.
What are hereditary diseases
This genetic diseases or chromosomal abnormalities, the development of which is associated with a disorder in the hereditary apparatus of cells transmitted through reproductive cells (gametes). The occurrence of such hereditary pathologies is associated with the process of transmission, implementation, and storage of genetic information. All more men have a problem with this kind of deviation, so the chance of conceiving healthy child is getting smaller. Medicine is constantly researching to develop a procedure for preventing the birth of children with disabilities.
Causes
Genetic diseases of hereditary type are formed by mutation of genetic information. They can be detected immediately after the birth of the child or later long time with long-term development of pathology. There are three main reasons for the development of hereditary diseases:
- chromosomal abnormalities;
- chromosome disorders;
- gene mutations.
The last reason is included in the group of hereditarily predisposed type, because their development and activation are also influenced by environmental factors. A striking example such diseases are considered hypertonic disease or diabetes. In addition to mutations, their progression is affected by prolonged overexertion nervous system, poor nutrition, mental trauma and obesity.
Symptoms
Each hereditary disease has its own specific symptoms. On this moment Over 1,600 different pathologies are known that cause genetic and chromosomal abnormalities. Manifestations vary in severity and brightness. To prevent the onset of symptoms, it is necessary to identify the likelihood of their occurrence in time. The following methods are used for this:
- Twin. Hereditary pathologies are diagnosed by studying the differences and similarities of twins to determine the influence of genetic characteristics and the external environment on the development of diseases.
- Genealogical. The likelihood of developing abnormal or normal traits is studied using a person's pedigree.
- Cytogenetic. The chromosomes of healthy and sick people are studied.
- Biochemical. Human metabolism is monitored and the features of this process are highlighted.
In addition to these methods, most girls undergo ultrasonography. It helps to determine, based on fetal characteristics, the likelihood of congenital malformations (from the 1st trimester), to suggest the presence of a certain number of chromosomal diseases or hereditary ailments of the nervous system in the unborn child.
In children
The vast majority of hereditary diseases appear in childhood. Each of the pathologies has its own symptoms that are unique to each disease. There are a large number of anomalies, so they will be described in more detail below. Thanks to modern methods diagnostics, it is possible to identify deviations in the development of a child and determine the likelihood of hereditary diseases while the child is pregnant.
Classification of hereditary human diseases
Genetic diseases are grouped based on their occurrence. The main types of hereditary diseases are:
- Genetic – arise from DNA damage at the gene level.
- Hereditary predisposition, autosomal recessive diseases.
- Chromosomal abnormalities. Diseases arise due to the appearance of an extra chromosome or the loss of one of the chromosomes or their aberrations or deletions.
List of hereditary human diseases
Science knows more than 1,500 diseases that fall into the categories described above. Some of them are extremely rare, but certain types heard by many. The most famous pathologies include the following:
- Albright's disease;
- ichthyosis;
- thalassemia;
- Marfan syndrome;
- otosclerosis;
- paroxysmal myoplegia;
- hemophilia;
- Fabry disease;
- muscular dystrophy;
- Klinefelter's syndrome;
- Down syndrome;
- Shereshevsky-Turner syndrome;
- cat cry syndrome;
- schizophrenia;
- congenital hip dislocation;
- heart defects;
- cleft palate and lip;
- syndactyly (fusion of fingers).
Which are the most dangerous?
Of the pathologies listed above, there are those diseases that are considered dangerous to human life. As a rule, this list includes those anomalies that have polysomy or trisomy in the chromosome set, when instead of two there are from 3 to 5 or more. In some cases, 1 chromosome is detected instead of 2. All such anomalies are the result of deviations in cell division. With this pathology, a child lives up to 2 years; if the deviations are not very serious, then he lives up to 14 years. The most dangerous illnesses are considered:
- Canavan disease;
- Edwards syndrome;
- hemophilia;
- Patau syndrome;
- spinal muscular amyotrophy.
Down syndrome
The disease is inherited when both or one of the parents has defective chromosomes. Down syndrome develops due to trisomy 21 chromosomes (instead of 2 there is 3). children with this disease suffer from strabismus, have abnormally shaped ears, a fold on the neck, and mental retardation and heart problems. This chromosome abnormality is not life-threatening. According to statistics, 1 out of 800 is born with this syndrome. Women who want to give birth after 35, the probability of having a child with Down increases (1 in 375); after 45 years, the probability is 1 in 30.
Acrocraniodysphalangia
The disease has an autosomal dominant type of inheritance of the anomaly, the cause is a violation in chromosome 10. Scientists call the disease acrocraniodysphalangia or Apert syndrome. Characterized by the following symptoms:
- violations of the ratio of the length and width of the skull (brachycephaly);
- High blood pressure (hypertension) develops inside the skull due to fusion of the coronary sutures;
- syndactyly;
- mental retardation due to compression of the brain by the skull;
- prominent forehead.
What are the treatment options for hereditary diseases?
Doctors are constantly working on the problem of gene and chromosome abnormalities, but all treatment is limited at this stage comes down to suppressing symptoms; complete recovery cannot be achieved. Therapy is selected depending on the pathology in order to reduce the severity of symptoms. The following treatment options are often used:
- Increasing the amount of incoming coenzymes, for example, vitamins.
- Diet therapy. An important point that helps to get rid of a number of unpleasant consequences of hereditary anomalies. If the diet is violated, a sharp deterioration in the patient’s condition is immediately observed. For example, with phenylketonuria, foods that contain phenylalanine are completely excluded from the diet. Refusal of this measure can lead to severe idiocy, so doctors focus on the need for diet therapy.
- Consumption of those substances that are absent in the body due to the development of pathology. For example, for orotaciduria, cytidylic acid is prescribed.
- In case of metabolic disorders, it is necessary to ensure timely cleansing of the body from toxins. Wilson-Konovalov disease (copper accumulation) is treated with d-penicillamine, and hemoglobinopathy (iron accumulation) is treated with desferal.
- Inhibitors help block excessive enzyme activity.
- It is possible to transplant organs, tissue sections, and cells that contain normal genetic information.
Rare genetic diseases are a very relative concept, because a disease may be practically non-existent in one region, but systematically strike in another area of the world most population.
Diagnosis of genetic diseases
Hereditary diseases do not necessarily appear from the first day of life; they can manifest themselves only after a few years. Therefore, it is important to do timely analysis for human genetic diseases, the implementation of which is possible both during pregnancy planning and during fetal development. There are several diagnostic methods:
- Biochemical. Allows you to determine the presence of a group of diseases associated with hereditary metabolic disorders. This method includes the analysis of peripheral blood for genetic diseases, as well as qualitative and quantitative examination of other biological fluids of the body.
- Cytogenetic. Serves to identify diseases that arise due to disturbances in the organization of cell chromosomes.
- Molecular cytogenetic. It is a more advanced method compared to the previous one and allows you to diagnose even the slightest changes in the structure and location of chromosomes.
- Syndromological. Symptoms of genetic diseases often coincide with signs of other, non-pathological diseases. The essence this method making a diagnosis consists of identifying from the entire range of symptoms specifically those that indicate a syndrome of hereditary disease. This is done using special computer programs and a thorough examination by a geneticist.
- Molecular genetic. The most modern and reliable method. Allows you to study human DNA and RNA and detect even minor changes, including in the nucleotide sequence. Used for diagnosing monogenic diseases and mutations.
- Ultrasonography:
- pelvic organs - to determine diseases of the reproductive system in women, causes of infertility;
- fetal development - to diagnose congenital defects and the presence of certain chromosomal diseases.
Treatment of genetic diseases
Treatment is carried out using three methods:
- Symptomatic. It does not eliminate the cause of the disease, but relieves painful symptoms and prevents further progression of the disease.
- Etiological. It directly affects the causes of the disease using gene correction methods.
- Pathogenetic. It is used to change physiological and biochemical processes in the body.
Types of genetic diseases
Genetic hereditary diseases are divided into three groups:
- Chromosomal aberrations.
- Monogenic diseases.
- Polygenic diseases.
It should be noted that congenital diseases do not belong to hereditary diseases, because they most often arise due to mechanical damage fetus or infectious lesions.
List of genetic diseases
Most common hereditary diseases:
- hemophilia;
- color blindness;
- Down syndrome;
- cystic fibrosis;
- spina bifida;
- Canavan disease;
- Pelizaeus-Merzbacher leukodystrophy;
- neurofibromatosis;
- Angelman syndrome;
- Tay-Sachs disease;
- Charcot-Marie disease;
- Joubert syndrome;
- Prader-Willi syndrome;
- Turner syndrome;
- Klinefelter's syndrome;
- phenylketonuria.
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 Caucasians and affects up to 80% of Asians, 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 English doctor John Down syndrome, which 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 clinical picture pathology in 1942. Together with endocrinologist Fuller Albright, he found out that if women normally have a pair of sex chromosomes XX, and men have XY, then when this syndrome males have 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 history of the descendants is widely known Queen of England Victoria from the Windsor dynasty. 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 latter's only son 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. Likely death due to respiratory failure.
According to the Russian branch of the American chemical and pharmaceutical corporation Abbott, the average life expectancy 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 are episodic or regular severe attacks of 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.
