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VERIFIED CONTENTAuthor: Krzysztof Bialazite

Genetic diseases are a large group of diseases related to abnormalities in the human genetic material. Find out what are the most common genetic diseases, how are the inherited genetic diseases that the mother can pass on to her baby, and can you protect yourself from genetic diseases?

Genetic diseasescan arise in many ways: some are inherited from parents, and others are caused by random mutations. The clinical picture of genetic diseases is diverse. Some genetic diseases are mild, but many of them can significantly affect everyday functioning.

Genetic diseases - types

The genetic material (genome) is a record of all features related to a given person. The information contained in the genetic material determines our appearance, personality traits, and to a large extent also our he alth.

A human's genetic material is found in every cell of his body, or more precisely - in the cell nucleus. Our genome is in the form of strands of DNA that can reach a length of 2 meters.

In order for DNA to fit inside a cell nucleus, it must be tightly packed. Properly twisted strands of DNA create chromosomes - the basic form of organization of human genetic material.

Each cell of our body has 46 chromosomes(23 pairs) - 44 "normal" chromosomes and 2 sex chromosomes. Sex chromosomes, according to their name, determine the sex of a person.Women have XX sex chromosomes and men have XY chromosomes .

Genetic diseases arise as a result of errors in the genetic material of a person. Abnormalities in the genome can range in size, ranging from minor mistakes in the genetic code to disorders of entire chromosomes. Changing the genetic material of a cell is called a mutation. A mutation may concern a single gene - the resulting disease is called monogenic.

If the disorder affects several genes at the same time, it is called a multi-gene disease. The most severe genome changes can involve entire chromosomes.

Changes in the number or structure of chromosomes are calledchromosome aberrations . The most commonA type of chromosomal aberration is Down syndrome, which consists in the presence of an extra chromosome in the 21st pair (the so-called trisomy 21).

Genetic diseases - when can they be inherited?

Is every genetic disease inherited from parents? The answer is no. Some genetic diseases are passed down from generation to generation, but there are also some that arise spontaneously (accidentally).

A genetic mutation may occur during the division of germ cells and the formation of an embryo. We are then talking about a de novo mutation: the child's genetic material will contain an error, even though the disorder did not occur in any of the parents.

For a genetic disease to be inherited, the mutation must be present in the germ cells of either parent. If there are abnormalities in the genetic material of the egg (from the mother) or the sperm (from the father), there is a risk of passing them on to the baby. The amount of this risk depends on the inheritance model of a given disease.

Diseases caused by a single gene mutation include dominant and recessive inheritance. In dominantly inherited diseases, one copy of the defective gene is enough for symptoms to develop. Recessively inherited diseases require two copies of the abnormal gene (so both parents must be carriers of the mutation to pass it on to their offspring).

Special rules apply to the inheritance of diseases that depend on the child's gender. We are talking then about sex-linked inheritance. These diseases concern the sex chromosomes: XX for a girl, XY for a boy. Basically, if the disease is inherited from the X chromosome, boys are at greater risk of developing the disease. They only have one copy of this chromosome and are therefore more likely to develop symptoms of the disease. For girls, there is also a second X chromosome.

Thanks to this, there is a chance that the girl will be a carrier of the mutation, but will not develop symptoms of the disease (the second, "he althy" chromosome will take over the dominant role). X-linked diseases are passed on in a unique way: the mother can pass the defective gene to both her sons and daughters, while the father only passes on to her daughters.

Analyzing families with diseases from this group, it can be noticed that women are mainly carriers of the disease (they do not have symptoms), and in men the disease manifests itself in a full-blown form.

Genetic diseases - ways of inheritance

The chance of passing on a genetic disease to your offspring depends on how you inherit the disease. Inheritance can be related to "normal" chromosomes (so-called autosomal) or to chromosomessexual. The disease may present with 1 copy of the defective gene (dominant inheritance) or 2 copies from both parents (recessive inheritance).

Combinations of these traits createfour disease inheritance models :

  • autosomal dominant : to develop the disease, it is enough for one of the parents to pass on the defective gene to the child. If one of the parents is sick, the child's risk of developing the disease is 50%. This group of diseases includes i.a. achondroplasia, polycystic kidney disease, neurofibromatosis.
  • autosomal recessive : the disease will only develop if a child receives faulty gene copies from both parents. If both parents are carriers of the mutation, the risk of passing the disease on to their child is 25%. In this way are inherited, inter alia, cystic fibrosis, phenylketonuria, spinal muscular atrophy.
  • sex-linked recessive : if a girl receives 1 copy of the defective gene, she will only be a carrier of the disease (will not develop symptoms). In the case of a boy, symptoms will develop. Such a model of inheritance concerns, inter alia, hemophilia, color blindness, muscular dystrophy.
  • Gender-linked Dominant : This is the rarest model of inheritance. 1 copy of the error on the X chromosome is enough to develop the disease, therefore both girls and boys suffer from the disease. In boys, the mutation may be lethal. An example of a disease inherited this way is Rett syndrome.

Most common genetic diseases

The most common diseases that a child can inherit from their parents are:

Achondroplasia

Achondroplasia is a genetic disease that leads to disturbances in the ossification process. The dominant symptom of achondroplasia is dwarfism. Achondroplasia is inherited autosomal dominantly - the risk of passing the disease to offspring by a sick parent is 50%.

Symptoms of achondroplasia can affect all bones in the human skeleton. Apart from short stature, there are also other skeletal defects:

  • shortening of limbs,
  • bad posture
  • and anatomical changes to the bones of the skull.

Polycystic kidney disease

Polycystic kidney disease is an inherited condition that causes numerous fluid-filled cysts to form in the kidneys.

In the course of the disease, cysts can also appear in other organs, most often in the liver and pancreas. Other typical symptoms of this disease are brain aneurysms and defects in the heart valves.

Polycystic kidney disease is the most common genetic kidney disease. Over the years, polycystic diseasekidney function can lead to gradual impairment of kidney function.

If your kidney function is completely lost, dialysis or kidney transplantation is often required.

Neurofibromatosis

Neurofibromatosis is a disease classified as phakomatosis, i.e. neurocutaneous diseases. Its symptoms mainly affect the nervous system and the skin.

In the course of neurofibromatosis, numerous stains of the "coffee and milk" type (the so-called cafe au lait stains) appear on the skin.

There are also numerous (benign) subcutaneous nodules - neurofibromas - all over the body.

This disease may lead to the development of neoplasms within the central nervous system (gliomas, meningiomas, neuromas), therefore patients should be under constant medical supervision.

Cystic fibrosis

It is a chronic disease affecting many organs, caused by mutations in the chloride channel in the mucous membranes. Cystic fibrosis is inherited in an autosomal recessive manner: development of the disease requires 2 copies of the defective gene from both parents.

The main symptoms of cystic fibrosis relate to the respiratory and digestive systems. The mucosa within the bronchi does not function properly - it produces thick mucus, which becomes an ideal environment for bacteria and is the cause of frequent respiratory infections.

In the digestive system, the secretion of digestive juices is disturbed, which can lead to malnutrition and growth disorders.

Treatment of cystic fibrosis is based on reducing the most troublesome symptoms of the disease. Patients require regular respiratory rehabilitation, prophylaxis of respiratory tract infections and the use of a high-energy diet.

Phenylketonuria

Like cystic fibrosis, it is an autosomal recessive disease. Phenylketonuria is caused by a disturbance in the processing of the amino acid phenylalanine. The genetic mutation causes an inactivity of the enzyme that converts phenylalanine to other compounds in he althy people.

In phenylketonuria, there is a significant increase in the concentration of phenylalanine in the body. Untreated phenylketonuria leads to brain damage and impaired mental development.

Currently in Poland, phenylketonuria is detected as part of general screening tests for newborns. An early diagnosis allows you to start treatment (a diet completely devoid of phenylalanine) from the first moments of life. In this way, the development of the symptoms of the disease can be completely prevented.

Spinal Muscular Atrophy

Spinal Muscular Atrophy is a disease that causes damagenerve cells of the spinal cord. Impulses from the spinal cord are not transferred to the muscles, which causes them to wane.

Patients with spinal muscular atrophy face significant motor disabilities - they are unable to stand or walk independently. Weakness of the respiratory muscles makes breathing difficult.

Spinal muscular atrophy is a disease for which breakthrough causal therapies have been developed relatively recently. In Poland, the drug Spinraza has been reimbursed since January 2022, which in the case of early activation is associated with a significant improvement in the he alth of patients.

The second drug used in spinal muscular atrophy is Zolgensma - the most expensive drug in the world (1.945 million euro for 1 dose). Zolgensma has been approved for use in the European Union since 2022, but has not yet been included in the list of reimbursed drugs in Poland.

Hemophilia

Hemophilia is a genetic condition that causes an impairment of blood clotting. Haemophilia is most often inherited in a gender-specific way: men get sick and women are asymptomatic carriers of the defective gene.

Blood clotting disorders in hemophilia lead to haemorrhages. Bleeding can be both external (most often from the nose) and internal (subcutaneous, intra-articular, intramuscular).

Treating haemophilia involves replenishing the missing clotting factors.

Color blindness

Color blindness is also known as color blindness. The essence of color blindness is the inability to distinguish colors. Color blindness, like hemophilia, is inherited in a gender-specific manner.

The cause of color blindness is the defect of the cones, i.e. the cells of the eye responsible for color vision.

Color blindness does not shorten life expectancy, but it does significantly affect everyday functioning. To date, no effective treatments for causal color blindness have been developed. However, there are special lenses available on the market that greatly improve your color vision.

Muscular dystrophy

Muscular dystrophy is a disease caused by a mutation in the dystrophin gene - one of the proteins in muscle cells. The most common form of the disease is Duchenne muscular dystrophy, which only affects men.

The main symptom of the disease is progressive muscle weakness, which leads to gradually increasing motor disability. People with muscular dystrophy lose their ability to walk by the age of 12.

A milder variant of the disease is Becker's muscular dystrophy, in which there is a change in the structure of dystrophin, not its totalloss.

Becker's muscular dystrophy is associated with a better prognosis, and patients remain physically active for longer. Unfortunately, no form of muscular dystrophy is treated causally - caring for patients is mainly based on intensive physical rehabilitation.

Rett syndrome

Rett syndrome is a disease with a special pattern of inheritance - dominant and sex-linked. Only girls suffer from this disease (in the case of boys, the mutation causes death at the stage of fetal development). The symptoms of Rett syndrome mainly affect the nervous system.

Rett syndrome occurs between 6 and 18 months of age. In the earliest stages of life, the child's development is normal; upon disclosure of the disease, there is a sudden deterioration of the neurological state.

The child loses the previously acquired motor and manual skills, speech and willingness to contact the environment disappear. Seizures are often an accompanying symptom. As of today, Rett syndrome remains an incurable disease.

Genetic diseases - is it possible to protect against them?

Genetic clinics deal with the issue of preventing genetic diseases. In the case of genetic diseases caused by specific gene mutations, it is not possible to avoid or reduce the risk of falling ill.

The goal of genetic counseling may be the early detection of genetic diseases, testing the carriage of defective genes, as well as the assessment of the risk of a specific genetic disease in the offspring.

Couples who deal with the problem of infertility or spontaneous miscarriages (it is believed that more than half of early miscarriages are caused by a genetic disorder in the fetus) are more and more often using genetic counseling.

Genetic diagnostics is also available as part of prenatal tests (non-invasive and invasive tests).

Early detection of genetic diseases significantly improves patients' prognosis in many cases. An example is phenylketonuria, which is diagnosed in the earliest stages of life and can be successfully treated with a proper diet.

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Genetic diseases