Features of the course of infectious diseases. General features of infectious diseases. Each acute infectious disease proceeds cyclically with a change of periods
Properties of a pathogenic microorganism.
pathogenicity(morbidity) - the ability
microorganism cause disease.
This is a species trait that manifests itself in
susceptible organism.
Pathogenicity is characterized specificity, i.e.
the ability of a microorganism to cause a certain
infection
Eg. MTB causes tuberculosis.
Pathogenicity is a trait that characterizes the species as a whole.
Eg. dysentery sticks are pathogenic, but within the species
there may be more or less pathogenic strains.
Virulence is the degree or measure of pathogenicity,
the individual property of this pathogen to cause
infectious disease.
This property, the species characteristic of each strain of pathogenic
organism.
All strains are divided into:
Moderately
Weak and avirulent.
Virulence is determined in laboratory animals by
the lethal dose least amount
pathogen or toxin that causes the death of all
animals infected with this dose.
And infectious dose- the minimum number of microbes,
capable of causing an infectious disease. Under
exposure to chemical, physical, biological
factors, a change in virulence is possible: weakening,
amplification, complete loss.
Factors of pathogenicity m / o.
1. Adhesion(adhesion) - the ability to attach to certain cells.
2. Colonization- reproduction on the surface of sensitive
3. Invasiveness- the ability to penetrate and spread in the tissues of the body.
4. Aggressiveness- the ability to resist the protective factors of the body.
a) antiphagocytic activity - the ability to resist phagocytosis associated with the capsule.
b) enzymes of aggression and invasion (hyaluronidase, collaginase), they allow m/o to penetrate through mucous membranes, connective tissue barriers, etc. Some m/o produce enzymes that destroy antibiotics, which determines their antibacterial resistance.
5. toxin formation- the ability of microbes to produce toxins.
Exotoxins- these substances of protein nature are secreted into
the environment with live m / o in the process
vital activity. Selectively act on certain
organs and tissues. Eg. tetanus toxin affects N.S.
Bacteria that produce exotoxin are called toxigenic.
Endotoxins- toxic substances that are part of the structure of bacteria are released when the microbial cell is destroyed. They do not have selective action, cause the same type of clinical picture (t, intoxication, diarrhea, cardiac disorders). Bacteria that contain endotoxins are called toxic.
The role of the macroorganism and the environment.
Properties M., affecting the infectious process:
resistance
Susceptibility
a) species
b) individual.
Susceptibility depends on age, gender, physical condition, hormonal status, and diet.
Physical, chemical and biological factors are indirectly involved in the development of the infectious process. They affect a person through the social conditions of life, the level of economic and cultural development, sanitary and hygienic conditions of work and life, national and religious customs, dietary habits, and preventive vaccinations.
Features of infectious diseases.
I. Specificity- pathogenic m / o causes its own disease and is localized in accordance with the pathogenesis of the disease.
II. contagiousness(contagiousness) - the ease (probability) of transmission of the pathogen from an infected organism to an uninfected one.
III. cyclicity- the presence of successively alternating periods of the disease, the duration of which depends on the properties of the m. and the resistance of M.
Periods of infectious diseases:
1) Incubation- from the moment of introduction of m. in M. until the onset of clinical manifestations of the disease.
2) Premonitory- the appearance of the first clinical manifestations of the disease (malaise, weakness, headache, increased t), there are no specific symptoms.
3) The period of pronounced clinical manifestations- there are specific symptoms.
4) Fading of clinical manifestations or period convalescence- cessation of reproduction of the pathogen in the patient's body, the death of the pathogen and the restoration of homeostasis.
IV. immune response- after the disease: immunity or increased sensitivity to the pathogen.
2. Contagiousness-infectiousness, the ability of a pathogen to cause disease
(the ability to transmit from an infected organism to an uninfected one), or the rate and intensity of infection. The contagiousness index is the percentage of cases from among those exposed to the risk of infection for a certain point in time.
3. Cyclicity- consecutive change of the periods of a disease. Sometimes, against the background of a complete clinical recovery, a person continues to release microorganisms into the environment - microbe carrier or carriage. It is divided into:
Ø Acute - up to 3 months.
Ø Prolonged - up to 6 months
Ø Chronic - more than 6 months
Ways of infection.
Infection with microorganisms can occur through damaged skin, mucous membranes (tissues of the eye, respiratory tract, urinary tract). Infection through intact skin is quite difficult, as the skin is a powerful barrier. But even the most insignificant injuries (insect bite, needle prick) can cause infection. If the mucous membranes are the entry gate for infection, then 3 mechanisms of pathogenesis are possible:
1. Reproduction of the pathogen on the surface of the epithelium.
2. Penetration of the pathogen into cells, followed by intracellular digestion and reproduction.
3. Penetration of the pathogen into the bloodstream and spread throughout the body.
Ways of infection.
The localization of the entrance gate depends on the method of infection, which is important. Like the plague!!! If infection occurs through a flea bite - crushing the flea and subsequent combing (contaminative), then a skin bubonic form occurs. If a
Infection occurs by airborne droplets, then the most severe form of plague develops - pneumonic. For causative agents of intestinal infections, the predominant transmission mechanism is fecal-oral, and the transmission route is alimentary. For respiratory diseases, the transmission mechanism is aerogenic, and the route is airborne.
The blood of a healthy person and animal is sterile, as it has strong antimicrobial properties due to the presence of humoral immunity factors (complement system), as well as cellular immunity factors (lymphocytic corporation).
But when an infectious process occurs in the blood, the causative agent of the disease or its metabolic products, toxins, appears and circulates for some time. It is through the blood that the infection spreads throughout the body - process generalization. The appearance of pathogens or toxins, i.e. foreign agents in large quantities in the blood is accompanied by fever, which is regarded as a protective reaction (the release of antibodies - immunoglobulins and other substances that trigger the body's immune response).
Ø Antigenemia is the circulation of foreign antigens or self-antigens in the blood and the release of antibodies to them. There is a formation of circulating immune complexes (CIC = Ag + Ab). These complexes are detected in the body using serological reactions.
Ø Bacteremia is the circulation of bacteria in the blood. It occurs as a result of the penetration of the pathogen into the bloodstream through the natural barriers of the body, as well as in transmissible infections after the bite of arthropods (typhus, relapsing fever, plague, tularemia). It ensures the transmission of the pathogen to another host, preserving it as a species. The cause of bacteremia can be surgical interventions, injuries, radiation sickness, malignant tumors, various severe forms of diseases caused by opportunistic bacteria.
Unlike sepsis and septicopyemia, in bacteremia, bacteria in the blood only circulate, but do not multiply. Bacteremia is a symptom of the disease and one of its stages. The diagnosis of bacteremia is made by isolating the culture of the pathogen or by infection through the blood of a sick laboratory animal.
Ø Viremia - the circulation of viruses in the blood.
Ø Sepsis or rotten blood is a severe generalized acute or chronic febrile human disease, caused by continuous or periodic entry into the blood of the pathogen from the focus of purulent inflammation. Sepsis is characterized by a discrepancy between severe general disorders and local changes and the frequent formation of new foci of purulent inflammation in various organs and tissues. Unlike bacteremia in sepsis due to a decrease in the bactericidal properties of the blood, the pathogen multiplies in the circulatory and lymphatic systems. Sepsis is a consequence of the generalization of localized purulent foci. The etiology of sepsis is diverse, frequent pathogens are staphylococci, streptococci, Gr (-) bacteria from the family of enterobacteria, meningococci, opportunistic bacteria, fungi.
Depending on the localization of the primary focus and the entrance gate of the pathogen, there are: postpartum, postabortive, peritoneal, wound, burn, oral, urosepsis, neonatal (infection can occur during labor and in fetal development), cryptogenic (the primary focus of purulent inflammation remains unrecognized ) and another.
Ø Septicopyemia is a form of sepsis, in which, along with intoxication of the body, purulent metastatic foci are formed in various tissues and organs, combined with the presence and reproduction of the pathogen in the circulatory and lymphatic systems.
Ø Toxinemia is the circulation of bacterial exotoxins in the blood. The pathogen itself is absent in the blood, but the target cells are affected by the products of its vital activity. Botulism, diphtheria are exotoxins, and tetanus is an anaerobic infection.
Ø Toxemia is the circulation of bacterial endotoxins in the blood. It is observed in severe forms of diseases caused by Gr (-) bacteria that have endotoxin, for example, in salmonellosis, escherichiosis, meningococcal and other infections. Often associated with bacteremia and sepsis.
The localization of the pathogen in the body also determines the ways of its excretion: with urine, feces, purulent discharge, sputum, saliva, mucus, blood, cerebrospinal fluid. Everything serves as material for diagnosis. Knowledge of the source of infection, the ways and means of infection, the properties of the pathogen, are the basis of anti-epidemic measures.
Table of contents of the subject "Infectious Process. Classification of Infections. Epidemiology of Infectious Process. Epidemic Process.":
1. Bacteriocarrier. The ability to long-term survival in the body. infectious process. Infection. Infectious disease.
2. Conditions for the development of infection. Pathogenicity. infectious dose. The rate of reproduction of microorganisms. Entrance gate of an infection. Tropism. Panthropism.
3. Dynamics of the infectious process. bacteremia. Fungemia. Viremia. Parasitemia. Sepsis. Septicemia. Septicopyemia. Toxinemia. Neuroprobasia.
4. Features of infectious diseases. The specificity of the infection. Contagiousness. Infection contagiousness index. Cyclicity. Stages of an infectious disease. periods of infectious disease.
5. Classification (forms) of infectious diseases. exogenous infections. endogenous infections. Regional and generalized infections. Monoinfections. Mixinfections.
6. Superinfections. Reinfections. relapses of infection. Manifest infections. typical infection. atypical infection. chronic infection. Slow infections. persistent infections.
7. Asymptomatic infections. abortion infection. Latent (hidden) infection. Inapparent infections. Dormant infections. Microcarrying.
9. Classification of infectious diseases according to Groboshevsky. population susceptibility. Prevention of infections. Groups of measures for the prevention of infectious diseases.
10. The intensity of the epidemic process. sporadic morbidity. Epidemic. Pandemic. endemic infections. Endemic.
11. Natural focal infections. Parasitologist E.N. Pavlovsky. Classification of natural focal infections. Quarantine (conventional) infections. Especially dangerous infections.
Features of infectious diseases. The specificity of the infection. Contagiousness. Infection contagiousness index. Cyclicity. Stages of an infectious disease. periods of infectious disease.
infectious diseases characterized specificity, contagiousness and cyclicity.
Infection specificity
Every infectious disease causes a specific pathogen. However known infections(for example, purulent-inflammatory processes) caused by various microbes. On the other hand, one pathogen (for example, streptococcus) can cause various lesions.
Contagiousness of an infectious disease. Infection contagiousness index.
contagiousness (infectiousness) determines the ability of the pathogen to be transmitted from one person to another and the rate of its spread in a susceptible population. For a quantitative assessment of contagiousness, it is proposed contagiousness index- the percentage of people who have been ill in a population for a certain period (for example, the incidence of influenza in a certain city for 1 year).
The cycle of an infectious disease
Development of a specific infectious disease limited in time, accompanied by a cyclical process and a change in clinical periods.
Stages of an infectious disease. periods of infectious disease.
Incubation period[from lat. incubatio, lie down, sleep somewhere]. Usually, between the penetration of an infectious agent into the body and the manifestation of clinical signs, there is a certain period of time for each disease - incubation period characteristic only for exogenous infections. During this period, the pathogen multiplies, the accumulation of both the pathogen and the toxins released by it occurs up to a certain threshold value, for which the body begins to respond with clinically pronounced reactions. The duration of the incubation period can vary from hours and days to several years.
prodromal period[from Greek. prodromos running ahead, preceding]. As a rule, the initial clinical manifestations do not carry any pathognomonic [from the Greek. pathos, disease, + gnomon, indicator, sign] for a specific symptom infection. Weakness, headache, feeling of weakness are common. This stage of an infectious disease is called the prodromal period, or "harbinger stage." Its duration does not exceed 24-48 hours.
The period of development of the disease. At this phase, individual features of the disease or signs common to many infectious processes are manifested - fever, inflammatory changes, etc. In the clinically pronounced phase, the stages of an increase in symptoms (stadium wcrementum), the heyday of the disease (stadium acme) and the extinction of manifestations (stadium decrementum) can be distinguished .
convalescence[from lat. re-, repetition of action, + convalescentia, convalescence]. The period of recovery, or convalescence as the final period of an infectious disease, can be fast (crisis) or slow (lysis), and also be characterized by a transition to a chronic state. In favorable cases, clinical manifestations usually disappear faster than the normalization of morphological disorders of organs and tissues and the complete removal of the pathogen from the body. Recovery may be complete or be accompanied by the development of complications (for example, from the side of the central nervous system, musculoskeletal system, or cardiovascular system). The period of final removal of the infectious agent may be prolonged and for some infections (eg, typhoid fever) may be weeks.
An infectious disease is a specific infectious condition caused by the introduction of pathogenic microbes and / or their toxins into the macroorganism, which interact with the cells and tissues of the macroorganism.
Features of the infectious process
1. The causative agent itself, that is, each m / o has its own disease.
2. Specificity , which lies in the fact that each pathogenic microbe causes "its own", inherent only to it, infectious disease and is localized in one or another organ or tissue.
3. Contagiousness (from lat. contaggiosus - contagious, contagious) means the ease with which the pathogen is transmitted from an infected organism to an uninfected one, or the speed with which microbes spread among a susceptible population using a chain reaction or fan-shaped transmission.
Infectious diseases are characterized by contagious period- the period of time during an infectious disease when the pathogen can spread directly or indirectly from a diseased macroorganism to a susceptible macroorganism, including with the participation of arthropod vectors. The duration and nature of this period is specific to the disease.
For a qualitative assessment of the degree of contagiousness, contagiousness index, defined as the percentage of people who become ill among those exposed to the risk of infection over a certain period of time.
4. Cyclic flow, which consists in the presence of successively changing periods based on the pathogenesis of the disease. The duration of the periods depends both on the properties of the microbe and on the resistance of the macroorganism, the characteristics of immunogenesis. Even with the same disease in different individuals, the duration of these periods may be different.
The following periods of disease development are distinguished: incubation (hidden); prodromal (initial); the period of the main or pronounced clinical manifestations of the disease (peak period); the period of extinction of the symptoms of the disease (early period of convalescence); recovery period (reconvalescence).
The period from the moment of introduction of a microbe (infection, infection) into a macroorganism until the onset of the first clinical manifestations of the disease is called incubation(from lat. incubo - rest or incubatio - without external manifestations, hidden). During the incubation period, the pathogen adapts to the internal environment of the infected macroorganism and overcomes the protective mechanisms of the latter. In addition to the adaptation of microbes, they reproduce and accumulate in the macroorganism, move and selectively accumulate in certain organs and tissues (tissue and organ tropism), which are most susceptible to damage. On the part of the macroorganism, already in the incubation period, its defenses are mobilized. There are no signs of the disease in this period yet, however, special studies can reveal the initial manifestations of the pathological process in the form of characteristic morphological changes, metabolic and immunological changes, the circulation of microbes and their antigens in the blood. In epidemiological terms, it is important that a macroorganism at the end of the incubation period may pose an epidemiological hazard due to the release of microbes from it into the environment.
Prodromal, or initial, period(from Greek. prodromes - a precursor) begins with the appearance of the first clinical symptoms of a general disease as a result of intoxication of the macroorganism (malaise, chills, fever, headache, nausea, etc.). There are no characteristic specific clinical symptoms on the basis of which an accurate clinical diagnosis could be made during this period. At the site of the entrance gate of infection, an inflammatory focus often occurs - primary effect. If at the same time regional lymph nodes are involved in the process, then they talk about primary complex.
The prodromal period is not observed in all infectious diseases. Usually it lasts 1-2 days, but can be shortened to several hours or lengthened up to 5-10 days or more.
The prodromal period changes perione of the main or pronounced clinicalmanifestations of the disease(peak period), which is characterized by the maximum severity of general non-specific symptoms of the disease and the appearance of specific or absolute (obligate, decisive, pathognomonic), symptoms of the disease characteristic only of this infection, which allow an accurate clinical diagnosis. It is during this period that the specific pathogenic properties of microbes and the response of the macroorganism find their most complete expression. This period is often divided into three stages: 1) the stage of increasing clinical manifestations (stadium incrementi); 2) the stage of maximum severity of clinical manifestations (stadium fastigii); 3) the stage of weakening of clinical manifestations (stadium decrementi). The duration of this period varies significantly with different infectious diseases, as well as with the same disease in different individuals (from several hours to several days and even months). This period may end fatally, or the disease passes into the next period, which is called period of symptom reliefdiseases (early period of convalescence).
During the extinction period, the main symptoms of the disease disappear, the temperature normalizes. This period is changing a period of convalescence(from lat. re - denoting the repetition of an action and convalescentia - recovery), which is characterized by the absence of clinical symptoms, the restoration of the structure and function of organs, the cessation of reproduction of the pathogen in the macroorganism and the death of the microbe, or the process can turn into microbe carrier. The duration of the convalescence period also varies widely even with the same disease and depends on its form, severity of the course, immunological characteristics of the macroorganism, and the effectiveness of the treatment.
Recovery can be complete, when all impaired functions are restored, or incomplete, when residual (residual) phenomena persist, which are more or less stable changes in tissues and organs that occur at the site of the development of the pathological process (deformities and scars, paralysis, tissue atrophy, etc.). d.). There are: a) clinical recovery, in which only the visible clinical symptoms of the disease disappear; b) microbiological recovery, accompanied by the release of the macroorganism from the microbe; c) morphological recovery, accompanied by the restoration of the morphological and physiological properties of the affected tissues and organs. Usually, clinical and microbiological recovery does not coincide with the complete recovery of morphological damage that lasts for a long time. In addition to complete recovery, the outcome of an infectious disease can be the formation of microbial carriage, the transition to a chronic form of the course of the disease, and death.
5. Formation of immunity, which is a characteristic feature of the infectious process. The intensity and duration of acquired immunity differ significantly in various infectious diseases - from pronounced and persistent, practically excluding the possibility of re-infection throughout life (for example, with measles, plague, natural smallpox, etc.) to weak and short-term, causing the possibility of re-infection diseases even after a short period of time (for example, with shigellosis). With most infectious diseases, a stable, intense immunity is formed.
The intensity of the formation of immunity in the process of an infectious disease largely determines the characteristics of the course and outcome of an infectious disease. characteristic featurepathogenesis of infectious diseases isdevelopment of secondary immunodeficiency. In some cases, an inadequately pronounced immune response aimed at localizing and eliminating the microbe takes on an immunopathological character (hyperergic reactions), which contributes to the transition of the infectious process into a chronic form and can put the macroorganism on the verge of death. With a low level of immunity and the presence of microbes in the macroorganism, exacerbations and relapses may occur. Aggravation- this is an increase in the symptoms of the disease during the period of extinction or the period of convalescence, and relapse- this is the occurrence of repeated attacks of the disease during the recovery period after the disappearance of the clinical symptoms of the disease. Exacerbations and relapses are observed mainly in long-term infectious diseases, such as typhoid fever, erysipelas, brucellosis, tuberculosis, etc. They occur under the influence of factors that reduce the resistance of the macroorganism, and may be associated with the natural cycle of microbial development in the macroorganism, such as, such as malaria or relapsing fever. Exacerbations and relapses can be both clinical and laboratory.
6. For the diagnosis of infectious diseases are used specificmicrobiological and immunological methodsdiagnostics(microscopic, bacteriological, virological and serological studies, as well as bioassay and skin allergy tests), which are often the only reliable way to confirm the diagnosis. These methods are divided into main and auxiliary(optional), as well as methods express diagnostics.
7. Application specific drugs, directed directly against a given microbe and its toxins. Specific preparations include vaccines, sera and immunoglobulins, bacteriophages, eubiotics and immunomodulators.
8. The possibility of developing microbial carriage.
Unlike somatic diseases, infectious diseases caused by pathogenic microorganisms are characterized by the following features:
ü specificity: each pathogenic microbe causes its own infectious disease and is localized based on pathogenesis in a particular organ or tissue;
ü contagiousness (contagiousness) - the ease with which the pathogen is transmitted from an infected organism to an uninfected one, or the speed with which an infection spreads among a susceptible population;
ü cyclicity: successively alternating periods of the disease, the duration of which depends on the properties of microbes and the resistance of the macroorganism.
Development of the infectious process:
1. The incubation period is the period from the introduction of an infectious agent into the body until the onset of clinical manifestations.
2. The prodromal period develops with the appearance of the first clinical manifestations of the disease (fever, malaise, headache, weakness). There are no specific clinical symptoms during this period.
3. The period of the main clinical manifestations (high) is characterized by the appearance of the most significant for the diagnosis of specific clinical and laboratory symptoms and syndromes.
4. Period of disease outcome:
ü recovery: characterized by the cessation of reproduction of the pathogen in the patient's body, the death of the pathogen in the patient's body and the complete restoration of homeostasis;
ü lethal outcome;
ü carrier.
Ticks
Their development is carried out by metamorphoses. A larva with three pairs of legs hatches from the egg, then the larva turns into a nymph with 4 pairs of legs, the reproductive system is not developed. After the second metamorphosis, the nymph turns into an adult - a sexually mature individual.
An adult tick feeds on the blood of cattle, wild ungulates, foxes, and dogs.
The dog tick is found in mixed deciduous forests across most of Eurasia, with a lifespan of 7 years.
The taiga tick is distributed in the taiga part of Eurasia from the Far East to Central Europe, the life span is 3 years.
The wide distribution of ixodid ticks has led to the spread of the taiga encephalitis virus over a vast area. The spread of the virus and its adaptation to different types of vectors and a large type of natural reservoirs contributed to the emergence of various strains that differ in the degree of virulence. The Far Eastern strain is highly virulent.
To avoid contracting tick-borne encephalitis, precautions should be taken, especially when walking in the forest in summer or late spring. It is advisable to wear deaf clothes with buttoned sleeves and a collar, and it is also obligatory to wear a headdress.
Tick Removal:
It is most convenient to remove with curved tweezers or a surgical clip. The tick is captured as close to the proboscis as possible. Then it is gently sipped and at the same time rotated around its axis in a convenient direction. After 1-3 turns, the tick is removed entirely along with the proboscis. If you try to pull out the tick, then there is a high probability of a rupture.
If there are no tools, then you can remove it with a loop from a coarse thread. With a loop, the tick is captured as close to the skin as possible and gently, staggering to the sides, is pulled out.
Oiling will not cause the tick to take out its proboscis. The oil will only kill him by clogging his breathing holes. The oil will cause the tick to regurgitate its contents into the wound, which can increase the risk of infection. Therefore, oil cannot be used.
After removal, the wound is treated with iodine or another antiseptic for the skin. But you don’t need to pour a lot of iodine, as you can burn the skin.
Hands and tools after removing the tick should be thoroughly washed.
If a head with a proboscis remains in the wound, then there is nothing terrible in this. A proboscis in a wound is no worse than a splinter. If the proboscis of the tick sticks out above the surface of the skin, then it can be removed by holding it with tweezers and unscrewing it. You can also remove it from the surgeon in the clinic. If the proboscis is left, then a small abscess appears, and after a while the proboscis comes out.
When removing a tick, do not:
Oil the tick
Apply caustic liquids to the bite site - ammonia, gasoline, and others. Burning a tick with a cigarette
Pull the tick sharply - it will break off
Poking around in the wound with a dirty needle
Apply various compresses to the bite site
Squeeze a tick with your fingers
The removed tick can be destroyed or left for analysis by placing it in a jar. If everything is normal, then the wound heals in a week.
3. Chromosomal diseases - Down's syndrome, Edward's syndrome, Patau's syndrome.
The chromosome complex of normal somatic cells of modern humans consists of 46 chromosomes (2n = 46). In the cells of a female individual, in addition to 44 autosomes, there is a pair of sex chromosomes XX, and in males - XY. Accepted formulas for the image: 46, XX; 46, XY.
Chromosomal diseases are a large group of congenital pathological conditions with multiple congenital malformations, the cause of which is a change in the number or structure of chromosomes. Chromosomal diseases result from mutations in the germ cells of one of the parents. No more than 3-5% of them are passed from generation to generation. Chromosomal abnormalities are responsible for approximately 50% of spontaneous abortions and 7% of all stillbirths.
All chromosomal diseases are usually divided into two groups:
1) anomalies in the number of chromosomes. This group includes three subgroups:
Diseases caused by a violation of the number of chromosomes,
Diseases associated with an increase or decrease in the number of sex X and Y chromosomes
Diseases caused by polyploidy - a multiple increase in the haploid set of chromosomes
2) violations of the structure (aberrations) of chromosomes. Their reasons are:
Translocations - exchange rearrangements between non-homologous chromosomes
Deletions - loss of a section of a chromosome
Inversions - rotations of a chromosome segment by 180 °
Duplications - duplication of a section of a chromosome
Isochromosomy - chromosomes with repeated genetic material in both arms
Occurrence of ring chromosomes - connection of two terminal deletions in both arms of a chromosome
Diseases caused by a violation of the number of autosomes
Down syndrome - trisomy on chromosome 21, the signs include: dementia, growth retardation, characteristic appearance, changes in dermatoglyphics (patterns on the skin of the palmar side of the hands and feet of a person). The syndrome was named after the English physician John Down who first described it in 1866. The connection between the origin of the congenital syndrome and the change in the number of chromosomes was revealed only in 1959 by the French geneticist Jérôme Lejeune. The frequency of births of children with Down syndrome is 1 in 800 or 1000. Down syndrome occurs in all ethnic groups and among all economic classes. The age of the mother affects the chances of conceiving a child with Down syndrome. If the mother is between 20 and 24 years old, the chance of this is 1 in 1562, between 35 and 39 years old it is 1 in 214, and over the age of 45, the chance is 1 in 19. Trisomy occurs due to the fact that chromosomes do not separate during meiosis. When fused with a gamete of the opposite sex, the embryo produces 47 chromosomes, and not 46, as without trisomy.
Patau syndrome - trisomy on chromosome 13, characterized by multiple malformations, idiocy, often - polydactyly, violations of the structure of the genital organs, deafness; Almost all patients do not live up to one year. Occurs with a frequency of 1:7000-1:14000. The survivors suffer from deep idiocy.
Edwards syndrome - trisomy on chromosome 18, the lower jaw and mouth opening are small, the palpebral fissures are narrow and short, the auricles are deformed; 60% of children die before the age of 3 months, only 10% live up to a year, the main cause is respiratory arrest and disruption of the heart. The population frequency is approximately 1:7000. Children with trisomy 18 are more often born to older mothers, the relationship with the age of the mother is less pronounced than in cases of trisomy chromosomes 21 and 13. For women over 45 years of age, the risk of giving birth to an affected child is 0.7%. Girls with Edwards syndrome are born three times more often than boys.