The genetic structure of a person is determined by 23 pairs of chromosomes, which differ in shape and size. The largest chromosome 1. It is almost 4 times the size of chromosome 22. 23 pairs are chromosomes X and Y. They determine the gender of people. In women, 23 pairs contain 2 chromosomes X, this pair is designated XX. In men, 23 pairs consists of their chromosomes X and Y, i.e. is a pair of XY.
When an embryo forms in the uterus of a future mother, it does not yet have any signs of a person, but 23 pairs of chromosomes already determine the sex of the future baby. The previous 22 pairs are called autosomes. They provide the development of all the internal organs and tissues of the baby.
Infertility as one of the signs of monosomy
Female infertility can be the result of various pathologies. In case of violation of the structure of 23 pairs of chromosomes, it is laid before birth, when the potential mother herself was in the state of the embryo in the womb.
If one chromosome X is missing or damaged in pair XX, this pathology is called monosomy X. Infertility is one of the most indicative signs of X monosomy. Modern medicine studies both the signs of this pathology and its treatment methods.
What it is?
Monosomy is a deviation named after the scientist who discovered it, Turner syndrome. This genetic disease occurs only in girls. According to statistics, it is found in about 1 out of 2500 cases.
At the moment, the development of medicine to prevent Turner syndrome is impossible. Girls with this pathology can lead a normal life, but they need the supervision of a doctor, as complications can develop.
Other signs of monosomy
It was revealed that girls with a probability of having a monosomy syndrome in childhood can have the following symptoms of the disease:
- In infancy, the arms and feet swell.
- Babies are behind their peers in height.
- The palate of such girls is higher than that of the average child, and the ears are lower.
- Sick girls are prone to gaining excess weight.
- Often there is flat feet.
- The eyelids hang low above the eyes.
- Strabismus.
- The neck is shortened.
- Hairiness of body parts is observed.
- Shortened hands.
In addition to these diseases, a teenage girl can be identified:
- Heart disease (non-closure of valve walls).
- Slowing the onset of puberty.
- Hearing problems.
- Frequent increase in blood pressure (hypertension).
- Persistent diseases associated with infections in the ears.
- Dry eyes.
- Violation of posture, up to scoliosis.
From the point of view of sexual development is observed:
- Disproportionality of the external genitalia.
- Underdevelopment of the mammary glands.
- No armpit and pubic hair.
- Underdevelopment of the uterus.
- Absence or passivity of the ovaries.
- Reduced content of female hormones.
- Menstrual passivity, up to the absence of menstruation.
The difficulty in diagnosing the symptoms is that the same symptoms can be observed with other diseases. If a girl of any age has them, it is necessary to undergo an examination in a clinic.
One of the characteristic signs of sex chromosome monosomy is an excess of skin on the sides of the neck, which forms longitudinal folds.
The causes of the appearance of monosomy
At this stage of the development of science, it was not possible to establish in detail the causes of the monosomy in the fetus. What is known for sure - pathology is not related to heredity. The main influence is exerted on the occurrence of pathology in the fetus by gene disorders of the father's germ cells during conception. This is the main cause of monosomy.
If the father’s genes underwent a mutation, the structure of the X chromosome was rearranged, in a child - girl, 23 pairs of chromosomes can also be damaged. But it should be noted that in such a family it is not worth putting an end to the birth of children. A father with a violation of the X chromosome is very likely to conceive and give birth to a completely healthy child.
Why does the X chromosome monosomy appear? The causes of this disease are being studied, but at this stage, medicine can say the following:
- The occurrence of monosomy in the fetus is not associated with adverse external conditions.
- This pathology is not inherited. Otherwise, all the girls in the family of a genetically injured father would receive it.
- The most likely cause of Turner syndrome is the effect of harmful factors on the father's germ cells shortly before conception.
- During the period of division of the zygote and its transformation into an embryo, disruptions can occur that are the cause of the mosaic type of monosomy.
Diagnosis of the disease
In order for the fetus chromosome monosomy to be excluded, even before delivery, women at risk are given a special genetic examination. This examination - prenatal genetic analysis - includes an ultrasound examination, a biopsy of the muscles and skin of the fetus, and a laboratory blood test.
The doctor prescribes such serious examinations when it comes to leaving the fetus or terminating the pregnancy. Therefore, they are prescribed in the first 3 months of pregnancy. That is, if the family does not solve the question of whether or not to be a child, examinations are not prescribed.
The doctor may recommend a genetic examination so that monosomy on chromosome 21 is excluded if:
- The expectant mother is over 35 years old.
- In the pregnant family, hereditary pathologies were observed.
- In the family, there were cases of brittle (fragile) X chromosomes.
- Suspicion of hemoglobinopathy.
- Suspicion of Down syndrome in a child and other unfavorable situations related to heredity.
When diagnosing, such moments are taken into account that the examination should not harm the health of the mother or child, it cannot lead to fetal loss. Diagnostic doctors are required to be highly qualified for diagnosis based on the results of the examination.
Before conducting a genetic examination, a woman must undergo a screening examination with a gynecologist in her clinic so that the doctor makes a decision whether the pregnant woman is at risk, that is, is there a chance that the fetus will reveal a monosomy syndrome. Only after a positive answer to this question is the pregnant woman sent for a genetic examination.
In prenatal diagnosis, there are other methods - puncture of the fetal bladder with the aim of taking amniotic fluid for analysis, taking blood from the umbilical cord, fetoscopy. The latter is the introduction of the probe and the examination of the fetus through it. Fetoscopy is used very rarely, because at the modern level of development of medical equipment, this procedure is successfully replaced by ultrasound.
If the fetus was not detected on time the X chromosome monosomy, and there was a suspicion of a diagnosis a few years after birth, the girl is examined in the following ways:
- The absence of sex chromatin is determined.
- A karyotype is determined.
- A consultation with a pediatric gynecologist is underway.
- Do an ultrasound of the internal genital organs.
- At the age of 9-10 years, a blood test for hormones is performed.
- An x-ray of the hands is prescribed to match the bone development with the age norm.
Based on the results of the survey, a special commission may decide on disability.
Types of Monosomy
Monosomy is a disease of various types. In a born girl, the second chromosome in pair XX may be completely absent. This type of genetics is designated as 45X0. These girls have completely absent or undeveloped ovaries and the uterus. Their puberty will not take place. There is no chromosome that determines the development of secondary sexual characteristics, the genitals themselves and the corresponding hormones.
If the second chromosome in the XX pair is present, the genetic type is 46 XY. In this case, the girl will have a uterus and ovaries, but they will have a rudimentary structure, that is, she will not be able to ovulate and conceive a child.
A much more dangerous case is when one chromosome is not enough in pairs 1 - 22. They are called autosomes. With the normal development of the zygote in each cell, 2 chromosomes are sent to its different poles. If one autosome is not enough, only the existing chromosome is sent to the cell pole. When it merges with a healthy one, a zygote is obtained with an abnormal number of chromosomes. This leads to the death of the embryo and spontaneous abortion. If the number of chromosomes is more than 1 than in the standard version, a miscarriage may not occur, but then a child is born who is unable to live long.
Partial monosomy
Partial monosomy is formed when the chromosome breaks down, as a result of which one whole and part of the second chromosome remain in the pair. The cause of the pathology is the structural chromosomal rearrangement of the sex cells of the parents in the period shortly before conception. The consequences of the disease depend on which particular chromosome has undergone partial destruction.
Feline scream syndrome
Destruction of a part of the chromosome in the 5th pair creates the “cat scream” syndrome. The larynx in a sick child is narrowed, the cartilage is soft, as a result of the baby’s crying resembles cat meow.
This type is also characterized by the baby’s muscular lethargy, moon-shaped face, mental underdevelopment and physical retardation compared to their peers. The child has an underdeveloped skull, a low ear, strabismus and vision problems. As a rule, such children suffer from heart defects. These patients do not live long - the term reaches no more than 10 years. A similar pathology is seen in 1 out of 45,000 cases.
Wolf-Hirschhorn Syndrome
A break in one chromosome from 4 pairs (Wolf-Hirschhorn syndrome) occurs in 1 out of 100,000 cases. Children who have a 4-pair chromosome monosomy are more likely to get it from young mothers and fathers. The weight of the child at birth is much less than the norm - about 2 kg. In infants, there is a delay in physical and mental development, motility is complicated very slowly. They suffer from underdevelopment of the skull.
According to external signs, it is possible to note the coracoid nose, the protruding forehead, the low landing of the ears, the longitudinal folds in front of the ears. They also have muscle lethargy. They hardly respond to external stimuli. Such children are prone to seizures. Outwardly, they may have an abnormal structure of the eyes, a small mouth with lowered lips in the corners, curvature of the feet. Sick children often suffer from heart defects. Affected by kidney disease. Most children with this chromosomal destruction do not live to see a year.
Orbeli Syndrome
A chromosome break of 13 pairs is called Orbeli syndrome. Children with this deviation are born with low weight - up to 2.2 kg. They have pathologies of almost all internal organs. Their skull is underdeveloped, there is no nose bridge - the forehead immediately passes into the nose. The nose has an increased width, the sky is high, the auricles are understated. The baby has a pathology of vision, underdevelopment of the musculoskeletal system. There may be no natural rectal canal and anus. Heart defects, kidney diseases, and brain pathologies are often observed. These children, as a rule, are oligophrenic, they suffer from cramps, they often lose consciousness. Babies do not live up to 1 year.
Monosomy is a very dangerous disease, while children with partial monosomy are extremely rare. Expectant mothers do not need to tune in to such a sad event.
Complications of Monosomy X
Women with monosomy X are prone to various diseases of the internal organs more often than genetically healthy people. They should be observed by a doctor and periodically undergo a medical examination.
A common complication is kidney disease. In sick women, infectious diseases of the genitourinary organs often arise, are incorrectly located, and the kidneys are not fully developed.
If a person has a monosomy, then sometimes the thyroid gland suffers, in which an insufficient level of hormones is produced that the body needs. The thyroid gland becomes inflamed, which is why these troubles occur. Treatment can only be taken with drugs that support normal hormonal levels. They must be prescribed by a doctor. Self-medication is unacceptable.
Those with Turner syndrome are prone to celiac disease. This pathology is expressed in the occurrence of an allergy to gluten protein. Patients should not eat wheat and barley products.
Complications can give any monosomy. The diseases that accompany monosomy can be different, for example, cardiovascular diseases. Women with pathology need the supervision of a cardiologist who will monitor the condition of their aorta and prevent the development of hypertension.
Because Turner Syndrome patients are prone to obesity, they may face diabetes.
Frozen pregnancy
Genetic pathologies, including fetal monosomy, are considered one of the reasons for the development of a dead pregnancy. This is the death of the fetus inside the womb. With monosomy, this happens before the 12th week of pregnancy. Sometimes the fetal life is longer - up to 20 weeks. This danger is threatened if the fetus does not have one of the chromosomes from pairs 1–22, this is the so-called trisomy. Monosomy is the reason for deliberate termination of pregnancy.
Trying to save the fetus with serious developmental abnormalities does not seem meaningful. Frozen pregnancy ends in a miscarriage. This risk affects women over the age of 35 - 40 years, as well as those who have had this before.
Scientists also noted a decrease in the life expectancy of women with monosomy, a tendency to atherosclerosis, tumors.
Monosomy treatment
Monosomy is a pathology that cannot be treated, but doctors are successfully coping with its consequences. The essence of the treatment is that an organism devoid of hormonal regulation by the ovaries needs artificial regulation. Pathology of internal organs is treated with medication or surgery. Comprehensive treatment includes:
- Growth hormone medications are taken by girls immediately after diagnosis.
- By the age of puberty, healthy children suffering from monosomy are prescribed sex hormones.
- Women with a pathology who want to bear a child are helped by reproductive medicine - the introduction of a donated fertilized egg with further monitoring of the course of pregnancy.
- Treatment of pathologies of internal organs with modern drugs and procedures.
- Psychological assistance to women in order to adapt them in a social environment, taking into account the characteristics of physiology.
The most important point in treatment is its timely start - immediately after a diagnosis. The second point is the consideration of the type of monosomy. If her type is 45X0, then a woman will not be able to have her child in any way. Psychological help should prepare her for the thought of adopting a child - an orphan.
The mosaic type of monosomy X - 46XY with the modern development of medicine makes it possible to bear your child. But he can be born sick. Adoption is more preferred in this embodiment.