Hereditary diseases are diseases caused by chromosomal and gene mutations. Some confuse hereditary diseases with congenital diseases. Indeed, congenital diseases, that is, diseases with which the baby is born, can be hereditary, but they can also be caused by some damaging external effect on the embryo or fetus – infection, ionizing radiation, toxic substance. On the other hand, not all hereditary diseases are congenital, since some of them can occur later, even in an adult. The appearance of a hereditary disease does not depend on external causes and is always due to a pathological mutation.
There are also diseases with a hereditary predisposition. These are diabetes mellitus, atherosclerosis, obesity, stomach and duodenal ulcers, etc. They can occur in a person whose relatives suffered from these pathologies, under the influence of external influences – malnutrition, lack of movement, severe stress (but this does not mean that this is necessary will happen).
Today, medicine knows about five thousand hereditary diseases – gene and chromosomal.
Most of all hereditary diseases are caused precisely by gene mutations. These include fermentopathy – various metabolic disorders. Enzymes, due to gene mutations, change their properties or are not produced at all by the body, and as a result, the biochemical reaction in which this enzyme is involved is not carried out.
Such hereditary diseases include phenylketonuria, homocystinuria, albinism, “maple syrup” disease (amino acid metabolism is impaired); galactosemia and fructosemia (disorders of carbohydrate metabolism); Tay-Sachs disease, plasma lipoidosis (impaired fat metabolism); Konovalov – Wilson’s disease (disturbances in metal metabolism); Lesch – Naihan disease (impaired purine metabolism).
Hereditary diseases can pass from generation to generation, such as phenylketonuria. With this disease, the body cannot absorb phenylalanine, the amino acid responsible for the formation of the hormones adrenaline, tyrosine, and norepinephrine. As a result, severe damage to the nervous system occurs, manifested by a violation of motor functions, dementia.
Marfan syndrome (arachnodactyly) is a hereditary disease of the connective tissue due to mutations in the gene responsible for the synthesis of fibrillin. The disease affects the musculoskeletal system, skin, eyes, cardiovascular system. People with Marfan syndrome are characterized by thinness, tall, long arms and legs (“spider-people”), they are characterized by dry skin, excessive joint mobility, deformations of the spine and chest. They suffer from heart defects, aortic aneurysm, subluxation of the lens. With intelligence, they are all right. Moreover, such outstanding personalities as Abraham Lincoln, Nicola Paganini, Charles de Gaulle, Corney Chukovsky suffered from Marfan syndrome.
Pathological mutations can occur during embryonic development. So, achondroplasia – a violation of bone growth and dwarfism – in 80% of cases is caused by a new mutation, while in the family no one has ever suffered from this disease.
Matrin – Bell syndrome (fragile X-chromosome syndrome) is also caused by a gene mutation. The disease is found in childhood and is characterized by mental retardation.
Most hereditary diseases manifest themselves in childhood, but gene mutations can make themselves felt in adulthood. So, Alzheimer’s disease, developing relatively early, at age 50, owes its appearance to a gene mutation.
These diseases are caused by chromosomal and genomic mutations, that is, a change in the structure or number of chromosomes. They usually appear during the formation of germ cells. Often such mutations lead to a miscarriage or the birth of a dead baby, in some cases the baby is born, but it turns out to be sick.
The well-known Down syndrome belongs to chromosomal diseases – in the chromosome set of such patients there is an extra chromosome. People with Down syndrome are characterized by a peculiar appearance, mental retardation, and reduced resistance to diseases.
Shereshevsky – Turner syndrome is a chromosomal disease that affects only women and consists in the absence of one sex chromosome. In such patients, the ovaries are underdeveloped, because of which the external sexual characteristics are smoothed out: they have low growth, broad shoulders, short legs, and a narrow pelvis. A characteristic feature is skin folds extending from the nape to the neck (sphinx neck). Mental development in such patients remains normal, but they are distinguished by emotional instability. Women with Shereshevsky-Turner syndrome do not have menstruation, and they cannot have children.
Shereshevsky – Turner Syndrome
Klinefelter’s syndrome is a male chromosomal abnormality. It consists in the presence of one or several female sex chromosomes in a man, which determines the “feminine” appearance of the patient — poorly developed muscles, narrow shoulders, and a wide pelvis.