The thymus gland is an important organ of the immune system, symptoms and treatment. Review of thymus diseases, causes of diseases and their consequences Thymic hyperplasia in children

The thymus, thymus or thymus gland in the human body is responsible for the formation of the immune system. Its development and growth continues until about the age of ten, after which it gradually decreases in size. Among the diseases of this organ, inflammation of the thymus gland, its hyperplasia or dystopia are most often noted. The information in our article will help you understand these conditions in more detail.

This important organ is located approximately in the chest area, most often immediately behind the pericardium. In childhood, the gland can shift to the area of the fourth rib, so during diagnosis, its location is immediately determined. The thymus gland is formed in the prenatal state; at birth, its weight can reach 10 grams. After three years, it begins to develop sharply, and reaches its maximum size (about 40 grams) by the period of adolescence at 13–15 years. After this, there is a gradual atrophy of its functions and a decrease in size. If this does not happen, and the thymus gland is detected in an adult, this is also an alarming symptom that requires treatment.

Why is the thymus gland needed?

Formation of the body's natural defense - the immune system.
Development of antibodies to viruses and bacteria.
Renewal of brain cells.

Disturbances in the functioning of this organ are fraught not only with a decrease in protective forces and frequent illnesses. In this case, we are talking about the appearance of autoimmune diseases, when the body “attacks” its internal organs. The risk of tumors and multiple sclerosis increases. Other symptoms of malfunction of this important organ are described below.

Major diseases of the thymus

It is incredibly difficult to diagnose such cases, because the symptoms are similar to other diseases. Persistent infections, increased fatigue and muscle weakness may indicate problems with the thymus. The final diagnosis can only be made by a doctor after examination. The specialist will also determine the true cause and type of problem.

The thymus or thymus gland is one of the most important organs of the immune system. It plays a special role in the normal development of the child. That is why the size of this endocrine organ in children is much larger than in an adult. Its decrease over time is called thymic involution. More details about this phenomenon later in the article.

Basic information

The thymus is located in the upper part of the chest cavity, in front of the trachea (breathing tube). It consists of two lobes connected by an isthmus. The organ reaches its maximum weight of 30-40 grams at the onset of puberty, after which its size gradually decreases.

The thymus belongs to both the group of immune organs and endocrine organs. That is, it performs a dual function: it participates in the synthesis of T-lymphocytes (white blood cells responsible for the normal immune response) and in the production of thymosin and thymopoietin, which, in turn, stimulate the formation of antibodies.

The role of the thymus in the child's body

The thymus performs its main function during the intrauterine development of the baby and after his birth at the age of 3 years. It is at this time that it actively synthesizes T-lymphocytes. This is necessary to protect the baby from infections, since the child’s body is most susceptible to the influence of pathogenic microorganisms.

The thymus produces the hormone thymosin, which is necessary for the normal formation of lymphocytes. As the function of the thymus gland decreases, the body's resistance to infection decreases. The child is susceptible to frequent respiratory diseases, which can easily become chronic.

With prolonged dysfunction of the thymus, an immunodeficiency state occurs. It is manifested not only by a decrease in resistance to pathogenic viruses and bacteria, but also to microorganisms that live inside each person, but in a normal state of immunity do not lead to the development of the disease. They are also called opportunists.

Main types of involution

Reduction in the size of the thymus can be of two types:

age;
accidental.

In both cases, the process of involution of the thymus consists of the gradual replacement of its tissue with fatty structures. This process is typical only for the thymus gland. No such changes occur either in the bone marrow or in the spleen.

Age-related changes

Age-related involution of the thymus is considered normal. It begins after the child reaches puberty. Its main manifestations are presented below:

reduction in organ weight;
decreased function, that is, inhibition of T-lymphocyte production;
replacement of normal organ tissue with fat.

Microscopic specimens of pathological anatomy show that thymus tissue during involution loses clear boundaries between the cortex and medulla. There is a gradual thickening of the partitions that separate the lobules from each other. Hassall's corpuscles (epithelial cells in the medulla of the thymus) become larger and their number increases.

After puberty, almost the entire mass of the thymus is replaced by adipose tissue. Only isolated islands of epithelial and reticular cells are noted. However, even in this form, the thymus continues to participate in the body’s immune response, producing T-lymphocytes.

Features of accidental changes

As noted earlier in the article, age-related and accidental involution of the thymus are two main types of reduction in the size of this organ. This section will discuss the second type of change in more detail.

The main difference between incidental changes in the thymus gland and age-related ones is that in the first case there is a decrease in the size of the lobules of this organ and a decrease in the number of lymphocytes. At the same time, with age-related involution, gland tissue is replaced by fat cells.

The term “accidental” was proposed back in 1969, but has not yet lost its relevance. Literally it means "accident". And indeed, in essence, accidental involution is a random response of the thymus gland to a harmful factor that has affected it.

Causes of pathology

The reasons why thymic involution begins are not fully understood. However, doctors identify a number of risk factors that increase the likelihood of developing these changes. These include:

radiation exposure;
taking antitumor drugs;
taking hormonal medications;
oncological diseases, primarily hemoblastosis (malignant neoplasms of the bone marrow);
infectious inflammatory diseases.

There are also studies on the importance of such conditions as hypothermia and hypoxia (decreased oxygen concentration in the body tissues) in the development of thymus pathology. However, their meaning is not exactly clear.

Main stages: first, second and third

When studying the pathological anatomy of accidental involution of the thymus, certain stages in the changes in the gland should be highlighted. Conventionally, there are five such stages, or phases.

The first phase is characterized by the absence of changes in the thyroid gland. The volume and structure of the thymus correspond to those of a healthy child.

In the second phase, a partial loss of lymphocytes occurs, which are localized in the cortical (outer) layer of the gland. Moreover, they are destroyed chaotically or in a “clustered” manner. Macrophages stick to these lymphocytes and “swallow” them. In the medical literature, this process is called phagocytosis. Some lymphocytes decrease due to their leakage into the general bloodstream.

In the third phase, the process progresses, and collapse of the reticular meshwork of the thymus gland develops. There are more lymphocytes in the medulla than in the cortex. As a result, when examining a microscopic specimen of accidental involution of the thymus under a microscope, the medulla appears darker, although normally it should be the other way around.

Also at this stage there is an increased synthesis of small thymic bodies. Normally, they are observed only in the medulla, and at the third stage of accidental involution they begin to populate the cortical part.

Main stages: fourth and fifth

In the fourth phase, the condition worsens even more. There is a loss of lymphocytes from the medulla, so distinguishing the cortical region from the medulla becomes extremely problematic. Thymic corpuscles unite with each other, which on a microscopic specimen looks like large cystic formations. These structures are filled with protein secretion with inclusions in the form of scales. Over time, this content leaves the cystic formations through

In the fifth (or terminal) phase, atrophy and hardening of the organ develops. This means that the thymus is significantly reduced in size, and the connective tissue partitions are thickened. There are very few lymphocytes; over time, almost the entire organ is replaced by connective tissue. Calcium salts are deposited in thymic bodies, which is called calcification or petrification.

Thus, during accidental involution the following processes occur in the thymus:

a sharp decrease in the size of the organ;
a significant drop in the functional activity of the thymus;
reduction in the number of lymphocytes up to their complete absence;
replacement of the thymus gland with connective tissue;
deposition of petrificates in thymic bodies.

Main symptoms

The main outcome of both complete and incomplete involution of the thymus is a decrease in its functional activity. With age-related changes, no symptoms develop, since this, in fact, is the norm for humans. And with accidental involution, when the decline in the function of the thymus gland occurs abruptly and manifests itself to a significant extent, certain clinical symptoms develop.

Common symptoms that develop regardless of the cause of the pathology include the following:

general fatigue, weakness;
an increase in the size of almost all groups of lymph nodes;
difficulty breathing - shortness of breath;
frequent colds and infectious diseases due to decreased immune resistance;
heaviness of the eyelids, feeling as if someone were pressing on them.

It is also common for a person to have clinical manifestations that correspond to a specific cause of thymic involution. For example, oncological diseases are characterized by the development of anemic syndrome, pallor or yellowness of the skin, decreased appetite, and weight loss. In inflammatory diseases, the patient is concerned about increased body temperature, chills, and deterioration in general condition.

Diagnosis of the disease

Making a diagnosis begins with a detailed questioning of the patient about his complaints, life history and illness. Thymic involution is not a definitive diagnosis. This is just one of the clinical manifestations of many pathological conditions. Therefore, the main task in diagnosing this process is to find its cause.

The involution itself can be seen using ultrasound (ultrasound), plain radiography of the chest organs. But ultrasound is a more reliable diagnostic method. It allows you to see the structure, size, shape of the thymus, the presence of pathological inclusions in it, and the relationship of the organ to the structures surrounding it.

They also do an immunogram. Using this examination method, you can see the number of different fractions of lymphocytes and thus assess the function of the thymus gland.

Conclusion

Involution of the thymus is a rather complex anatomical process that requires special attention. After all, the thymus performs a very important function - it provides human protection from foreign microorganisms. Fortunately, if the cause is addressed in a timely manner, this condition is reversible. Thyroid function may be restored. The main thing is to recognize the problem as early as possible in order to promptly contact a specialist who will prescribe effective treatment.

A decrease in immune strength and the body's resistance to external influences is often caused by endocrine disorders, in particular pathology of the thymus gland. This organ is responsible for the formation of T-lymphocytes, and therefore forms human immunity. For what reasons does the thymus gland perform poorly in children, as well as the main methods of treating such conditions are discussed in the information in our article.

The formation of this organ occurs during intrauterine development. At the time of birth, the thymus gland or thymus reaches 15 grams and continues to increase until adolescence. After this, its development slows down and in the adult body the thymus gradually atrophies.

The location of the thymus gland in newborns is located approximately in the middle of the chest, with the edge reaching the root of the tongue. There are rare situations where the thymus is located in the area of the fourth rib. Almost all pathological conditions associated with the location or size of the thymus gland affect the ability of the immune forces to resist disease.

Symptoms of thymus problems:

Muscle weakness.
Susceptibility to frequent colds.
Additional problems with the functioning of the thyroid gland.
Breathing disorders.
Increased size of lymph nodes.
Heart rhythm disturbances.
Pathologies of the reproductive organs.
Problems with excess weight.
Enlarged tonsils and adenoids.
Excessive sweating.
“Marble” pattern on the skin.
Cold extremities.

Of course, the detection of one or even several of the above symptoms does not constitute an accurate diagnosis. In any case, an additional examination and consultation with doctors in the direction will provide more information, as well as allow us to agree on appropriate treatment.

Pathologies of the thymus in children

If a baby has an enlarged thymus gland, this symptom does not mean that there will necessarily be problems in subsequent development. Typically, pathologies of this organ are detected during parallel examination. The enlargement, abnormal position or absence of the thymus is best seen on an x-ray, but it is also advisable to do an ultrasound examination to confirm the diagnosis.

The thymus in children is one of the main organs of the immune system. It is located behind the sternum between the lungs, above the heart.

Synonymous names - thymus gland, thymus gland, gland of “childhood”. Thymus - because it is similar in shape to the Latin letter V. Goiter - presumably because it is located near the thyroid gland.

The main task of the thymus in the body is to ensure the maturation, differentiation and immunological “training” of T-lymphocytes.

T-lymphocytes are blood cells responsible for the body's immune response to the introduction of antigens. Antigens are organisms (bacteria, protozoa, viruses, etc.), bodies or substances foreign to the body, which can cause harm to the body and which need to be neutralized.

Enlargement of the thymus gland or thymomegaly is a pathology in which the size and weight exceed the normal values typical for a certain age of the child.

Before we talk about enlargement of the thymus, we will find out what size of this gland is considered normal. By the way, it changes in size and weight in a person with age.

When a child is just born, the weight of the thymus gland is on average about 12 g. Then the child grows, and the thymus gradually increases. By the age of puberty (approximately 15 years), his normal weight is about 30 g.

Since the main task of the thymus is to educate and train immunological cells, it is in childhood that it is most needed, when children first encounter bacteria and viruses.

Once puberty ends, the thymus gland begins to involute (atrophy). Already by the age of 25 years, the weight of the thymus is on average 25 g. By the age of 60, it weighs approximately the same as a newborn child weighed - 12-15 g. And in a 70-year-old person it weighs only about 6-7 g.

Now let's return to the enlargement of the thymus gland in young children.

This problem occurs mainly in children under one year of age. Cases of thymomegaly are reported more often in boys than in girls.

What provokes the development of thymomegaly?

Various factors can provoke an enlargement of the thymus. These can be exogenous (external environmental factors) and/or endogenous (internal factors of the body) factors.

Such factors may be:

Aggravated obstetric and gynecological history of the pregnant woman (recurrent miscarriage, abortions)
Diseases of the mother during pregnancy - gestosis, infectious diseases, Rh conflict between mother and baby, late pregnancy and others.
The birth of a baby ahead of schedule.
Negative effects on the unborn child (alcoholism and nicotine addiction of the mother, X-ray exposure, taking unauthorized medications during pregnancy).
Pathologies of the newborn - birth injuries, sepsis, asphyxia, jaundice and others.

In a slightly simplified way, the fact that the thymus gland is enlarged can be explained by the fact that it has to actively perform the function of immune defense even before birth or immediately after birth.

The load on the gland exceeds its capabilities. Therefore, it increases in size to cope with the task. But, as a rule, even the enlarged gland fails to cope with the task, and its lymphoid tissue degenerates...

Since, in fact, an enlargement of the thymus gland is not the cause of the pathology, but a consequence, it is clear that, in addition to the enlargement of the thymus, there may be many other problems in the body of such a child.

What external manifestations can you notice in a baby with thymomegaly?

Babies with an enlarged thymus gland are characterized by high birth weight, increased appetite and rapid weight gain in the future. At the same time, their muscle tone is reduced and the muscles themselves are poorly developed. Such children usually have large facial features, a curvy body and broad shoulders.

Patients with thymomegaly have weak pigmentation, so they have pale skin, very light eyes and hair. When screaming or crying, infants experience blueness of the lips or nasolabial triangle. Doctors call this skin cyanosis.

A bright vascular pattern can be seen on the skin. In other words, a venous network is visible on the chest, abdomen, and back, which gives the skin a so-called marble pattern.

Such children are characterized by increased sweating, so their feet and palms are often wet and cold.

If the thymus is significantly enlarged, it puts pressure on neighboring organs. Therefore, newborn babies with thymomegaly often regurgitate. They also cough without symptoms of a cold, since the thymus puts pressure on the trachea.

In children with an enlarged thymus gland, there is hypertrophy of other types of lymphoid tissue involved in providing immunity: tonsils, adenoids, lymph nodes.

Often, girls with thymomegaly experience hypoplasia or underdevelopment of the genital organs, and in boys, the testicles do not descend into the scrotum at the time of birth.

How to determine an enlarged thymus?

First of all, the pediatrician or specialists study the mother’s medical history and how the pregnancy proceeded. The characteristics of the baby’s newborn period and its anthropometric data (weight, height, monthly weight gain and height) are also analyzed.

The doctor will be able to verify the diagnosis only after conducting an examination. The following diagnostic methods will help him with this.

1. Chest X-ray

It allows you to determine the size of the thymus gland and the degree of its enlargement. The doctor can do this by calculating the cardiothymycothoracic index (CTTI) on the image.

So, with 1st degree thymomegaly, the CCTI is 0.33 – 0.37. The second degree of increase is indicated by CCTI from 0.37 to 0.42. The range of CCTI for the third degree of thymomegaly is 0.42 – 3.

2. Ultrasound examination

This method allows you to determine the mass, volume and location (using a 3D sensor) of the thymus gland. During an ultrasound, not only the thymus gland is examined, but also the abdominal organs and adrenal glands.

3. Immunogram

With thymomegaly, there is a reduced number of mature T-lymphocytes and a weakening of their functional activity, a decrease in immunoglobulins of class G and A.

Children with suspected thymomegaly should be examined by a pediatrician together with an immunologist or endocrinologist.

What danger does an enlarged thymus gland pose?

A significant increase in the thymus gland can provoke the development of autoimmune and allergic diseases. Also, this pathology can become an impetus for the development of endocrine disorders in the child’s body, which can manifest itself as obesity and diabetes.

It has also been proven that children with an enlarged thymus gland have a much higher risk of sudden infant death syndrome.

Due to hypertrophy of lymphoid tissue with thymomegaly, infectious diseases can be complicated by otitis media or abdominal pain (enlarged intra-abdominal lymph nodes). Children are often diagnosed with heart rhythm disturbances.

Due to reduced immunity, such children are more likely to experience colds and various infectious diseases.

Treatment of thymomegaly

A slight enlargement of the thymus gland does not require specific treatment. With the first and second degrees of thymomegaly, parents and doctors need to provide dynamic monitoring of the child and simply be vigilant regarding the baby’s health.

Parents are advised to adhere to all the rules of a healthy lifestyle: breastfeeding at least in the first year of the baby’s life, sufficient physical activity of the child, limiting contact with infectious patients.

Drug treatment of thymomegaly in children is prescribed when there is a significant enlargement of the gland, when complications of this disease are observed. In severe cases of the disease, the issue of surgical intervention is decided individually.

In preparation for surgery and in case of serious health problems associated with thymomegaly, a course of glucocorticosteroids is prescribed.

For children with thymomegaly, an individual course of adaptogens and natural immune stimulants (eleutherococcus or ginseng) is recommended to correct immunity.

Children with an enlarged thymus gland are monitored by a pediatrician, endocrinologist and immunologist. And only specialists, based on an individual approach, decide on treatment tactics for a particular patient. Do not self-medicate.

Most often, with proper treatment and good care for the child, the problem is solved and recovery occurs.

Thymomegaly and vaccination

With thymomegaly, the child’s immune system is greatly weakened. Therefore, parents are concerned about the issue of vaccination of such children.

On the one hand, they cannot be left without protection from common infections. On the other hand, vaccination is a temporary additional burden on the child’s immune system.

That is, after the vaccine is administered, some minimal manifestations of the disease for which the vaccine was vaccinated appear in the body. A healthy baby can easily cope with these minimal manifestations, gain immunity and will not suffer from this disease in the future.

Is there a guarantee that the introduction of the vaccine will not provoke a deterioration in the health of an already weakened baby, that his body will cope with the load?

In all other cases, vaccination is acceptable. But the question of the possibility of vaccination in a particular patient should always be decided by the attending physician.

Parents cannot and should not decide this issue on their own. And even the most experienced doctor cannot give recommendations on this matter in absentia, without a comprehensive examination of the child.

Summary: enlargement of the thymus gland is a serious pathology that has a favorable prognosis with timely detection and properly selected treatment.

As a rule, by the age of six years of a child’s life, all signs of pathology disappear without a trace. But these 6 years are a serious test for a child with thymomegaly and his parents. And all these years, attention, common sense and patience are required from the parents and the pediatrician observing the child.

A practicing pediatrician and twice-mother, Elena Borisova-Tsarenok, told you about thymomegaly in children.

The thymus (thymus or thymus gland) is the primary organ of immunity, which can be considered the main, central organ of immunogenesis. In addition, it is an organ of hematopoiesis.

The thymus gland is located near the thyroid gland, for which it received one of its names. More precisely, by going down 2 fingers below the jugular notch you can determine the location of the thymus. It has several names: the thymus gland is called because of its similar shape to a two-pronged fork. Its third name, thymus, translated from Greek means “life force.”

It received this name because it is where T-lymphocytes mature and train to fight pathogens. In addition, lymphocyte differentiation occurs here.

This learning of lymphocytes occurs most actively in the first 3 years of life, and by 5 years its function begins to decline. This is noted due to the fact that immunity by this time has already become independent due to its complete formation.

At the age of 30, the function is almost not felt and is absent; after 40 years, the smallest part of the thymus remains. Age-related involution of the thymus occurs.

What is the gland responsible for?

In addition to fighting viruses in children, the thymus plays an equally important role in adulthood. Some researchers also call it the happiness point, since it is closely related to the production of endorphins.

If you can learn to activate it with the help of special exercises, then you will be quite capable of getting rid of stress and anxiety and managing your mood. Moreover, such an exercise for 2-3 hours will keep your mood feeling happy. When the thymus gland cannot function fully due to pathology, it increases in size, becoming like a butterfly.

Structure of the thymus

The gland has a loose consistency of gray-pink color; its morphology consists entirely of epithelial cells. It is surrounded by a dense capsule that extends deep into the substance of the gland with separate partitions and divides it into lobules or segments.

There are only 2 large lobes, they are fused with each other or tightly close to each other. The gland appears to be widened at the top and narrowed at the bottom, resembling the Latin letter V.

Each lobe contains its own medulla and cortex. The cortex contains immune cells and epithelial cells.

The latter have 3 varieties:

supporting;
hormone-producing (stellate);
cells that envelop T lymphocytes for their maturation (nanny cells).

Immune cells consist of immature lymphocytes, dendrites and macrophages. Already mature lymphocytes are all contained in the medulla; they are ready to enter the bloodstream. In addition to them, the medulla contains macrophages, supporting cells and stellate cells.

There are also small capillaries and lymph vessels. It is the capillaries that receive mature lymphocytes and carry them into the general bloodstream. And some lymphocytes are captured by lymphatic vessels and delivered to the lymph nodes and spleen.

The size of the gland in newborns is 5x4 cm and weighs 15 g. The gland grows before the start of puberty, and reaches 37 g. From 3 to 20 years, the weight of the gland remains relatively stable. Then regression or involution of the thymus gland begins.

In old age, the thymus is almost indistinguishable from the adipose tissue of the mediastinum and at 75 years old weighs only 6 grams. The white color is replaced by a yellowish color. It must be said that no other organ of the immune system undergoes age-related involution - this is a feature of the thymus. But even in a state of involution, the thymus continues to function in adults.

Thymus in children

In children, the thymus plays a very important role. At the age of up to one year, it is he who protects the child’s body from infections. Often in children the thymus gland becomes enlarged, but this does not mean an increase in its strength. On the contrary, such a child becomes susceptible to frequent diseases.

Thymus in adults

Supports 2 types of immunity: cellular and humoral. Humoral identifies and rejects pathogens; This is carried out by proteins - antigens in the blood. Cellular immunity is responsible for the synthesis of antibodies.

Regulation of the gland

The work of the thymus gland is regulated by GCS of the adrenal cortex and humoral immunity factors - interferons, lymphokines, interleukins; they are synthesized by other immune cells. GCS have the ability to suppress not only immunity, but also a number of functions of the thymus gland. In addition, they simply cause its atrophy.

Also, thymus atrophy increases under the influence of sex hormones. But pineal gland peptides slow down the process of involution of the thymus and can even cause its rejuvenation (this is melatonin).

What is the job of the thymus?

The work and main concern of the thymus gland is to successfully bring T-lymphocytes to maturity and their proliferation, which improves immunity. The formation of lymphocytes is preceded by the so-called. precursor cells; they are produced in the red bone marrow and are the founders of lymphocytes. In addition, the thymus produces hormones.

During various shocks (hypothermia, hunger, stress), T-lymphocytes are destroyed in large quantities and the functionality of the gland decreases - this is a temporary or rapid involution of the thymus.

The thymus also provides: replenishment of the body's energy reserves along with the thyroid gland; accelerates the breakdown of carbohydrates; increases the function of the pituitary gland and thyroid gland; actively helps in the exchange of BZHU, regulates the functioning of minerals and vitamins.

Enhances protein synthesis and thereby accelerates the growth of osteoblasts. Slows down central nervous system processes; slows down the pulse. The thymus also performs a drainage function - it collects and deposits all the lymph coming from the lymphatic vessels.

Thymic lymphocyte fractions

T-lymphoblasts, under the influence of thymic hormones and nurse cells, mature and divide into the following fractions:

Killer T cells– their job is to detect and eliminate any infected particle or cell.
T helper cells– work to enable killer T cells to detect pathologically infected cells. In addition, they produce cytokines - these are the signal molecules that trigger immune mechanisms.
T-suppressors– are fully responsible for the duration and intensity of immunity.

If the thymus begins to fade ahead of time, this leads to a decrease in immunity. The production of biologically active substances necessary for immunity ceases.

Accidental involution

In the entire lymphoid system, the thymus is the most labile. Such possible reactive changes were noticed in 1929 by the Swedish anatomist A. Gammar and called by him accidental involution (from the Latin accidents - chance).

But we are not talking about random involution, but about the randomness of the cause, while the response of the thymus is natural and stereotypical. Thymus hormones do not take part in this response. The thymus response to stress is combined with the involvement of the adrenal glands in the process. It acts indirectly through the hypothalamic-pituitary-adrenal system.

Its participation in this case boils down to the fact that mature T-lymphocytes are released into the blood against the background of increasing decay of immature cortical lymphocytes. The functionality of the thymus decreases and this is due to the effects of corticosteroids.

In 1969, J. Lashene and E. Stalioraityte proposed the term “accidental transformation” of the thymus, which is more successful and is used in domestic medicine. This term reflects the ability of the thymus to regenerate.

This phenomenon of accidental involution can occur for the reasons indicated above, as well as during irradiation, taking hormones and cytostatics; for childhood infections; hematological malignancies and oncology.

Accidental involution of the thymus differs from physiological age-related; With it, the thymus lobules become smaller, which means the volume of the gland decreases.

The number of lymphocytes in the gland's cortex drops so much that organ collapse occurs. But such phenomena are temporary - this is also different from age-related involution. Conventionally, this entire process in iron fits into 5 phases:

Phase 1- state of rest of a healthy baby’s organ.
Phase 2— the decrease of cortical lymphocytes in the nests begins (gland structure). They stick to macrophages and are absorbed by them. Some lymphocytes enter the bloodstream. In the cortex, the number of macrophages increases, which under a microscope resemble a picture of a “starry sky.” The production of the hormone interleukin I also increases.
Third phase– the number of lymphocytes continues to decrease and continues, which becomes the beginning of collapse (compression) of the reticular lobular network. In the medulla, the number of lymphocytes begins to predominate; this is called layer inversion. Under a microscope, therefore, this medulla appears darker after staining. The reticuloepithelium seems to wake up and begin to urgently become active. A huge number of Hassall's bodies (small thymic bodies) are formed; they not only fill the medulla, but also move into the cortex. They often contain disintegrating lymphocyte particles.
During phase 4– collapse of the gland occurs, i.e. its complete decline continues to increase; the difference between both layers – cortical and cerebral – is erased. Due to their quantity, the cells simply begin to merge and form cystic formations. They are quite large and can pour their contents into the capillaries of the lymphatic system in each lobule, which have already been mentioned, and from there they pass into larger vessels - large lymphatic vessels.
At the last, 5th stage- atrophy of the thymus occurs, which is acquired. The thymic lobules themselves are compressed and turned into narrow cords. Fibrous bridges, on the contrary, expand and swell. There are few lymphocytes left. Thymic bodies also become small and homogeneous in content. They are then calcified. This is explained by the fact that they lose their ability to empty into the lymphocapillaries of the thymus. Because of this, their contents thicken and calcium salts precipitate in them. Such acquired atrophy and involution is equivalent to a state of immunodeficiency.

During accidental involution, a developing decline in the mass and volume of the thymus occurs; its activity also drops even to the point of complete exhaustion.

The pathogenesis of accidental involution is very complex, and even today is not fully understood. But the fact of possible regeneration of the gland after such a phenomenon has already been revealed today.

In parallel with this, there is a growth of T-lymphocytes in the blood during the period of convalescence in any patient. In other words, accidental involution of the thymus gland with all its decline is reversible.

Regeneration of the thymus after accidental involution begins quite quickly, after 3-4 days and is accompanied by an increase in mitosis, resulting in complete and rapid recovery.

The thymus is populated with lymphocytes from the bone marrow. When part of its tissue is lost, the thymus loses its ability to recover completely. It not only cannot regenerate, but also cannot hypertrophy. For thymus regeneration, preservation of the reticuloepithelial stroma is mandatory.