Hereditary Diseases

Hereditary diseases are a large group of human diseases caused by pathological changes in the genetic apparatus. Currently, more than 6 thousand syndromes with a hereditary transmission mechanism are known, and their total frequency in the population ranges from 0.2 to 4%. Some genetic diseases have a certain ethnic and geographical prevalence, while others occur with the same frequency all over the world. The study of hereditary diseases is mainly in the competence of medical genetics, but almost any medical specialists can face such a pathology: pediatricians, neurologists, endocrinologists, hematologists, therapists, etc.

Hereditary diseases should be distinguished from congenital and familial pathology. Congenital diseases can be caused not only by genetic, but also by unfavorable exogenous factors affecting the developing fetus (chemical and medicinal compounds, ionizing radiation, intrauterine infections, etc.). However, not all hereditary diseases manifest themselves immediately after birth: for example, signs of Huntington’s chorea usually first manifest themselves at the age of over 40 years. The difference between hereditary and familial pathology is that the latter may be associated not with genetic, but with social or professional determinants.

The occurrence of hereditary diseases is caused by mutations – sudden changes in the genetic properties of an individual, leading to the appearance of new, non-normal signs. If mutations affect individual chromosomes, changing their structure (due to loss, acquisition, variation in the position of individual sites) or their number, such diseases are referred to as chromosomal. The most common chromosomal abnormalities are Down syndrome (trisomy on chromosome 21), Edwards syndrome (trisomy on chromosome 18), Klinefelter syndrome (polysomy on the X chromosome in men), Shereshevsky-Turner syndrome, cat cry syndrome, etc.

Hereditary diseases caused by mutations at the gene level belong to gene diseases. They can be monogenic (caused by mutation or absence of individual genes) or polygenic (caused by changes in many genes). Among monogenic diseases, there are pathologies with an autosomal dominant type of inheritance (Marfan syndrome, Recklinghausen’s disease, Ehlers-Danlos syndrome, osteogenesis imperfecta, Albright’s disease, etc.), autosomal recessive transmission (phenylketonuria, galactosemia, ichthyosis, progeria) and hereditary diseases linked to gender (hemophilia, phosphate diabetes, Duchenne muscular dystrophy, Hunter syndrome, Fabry’s disease).

Polygenic diseases are multifactorial in nature, i.e. a combination of genetic and environmental factors is important in their occurrence. These diseases are often treated as diseases with a hereditary predisposition. This group includes atherosclerosis, hypertension, diabetes mellitus, gastric ulcer and duodenal ulcer, allergic pathology.

Hereditary diseases can manifest themselves both immediately after the birth of a child, and at different stages of life. Some of them have an unfavorable prognosis and lead to early death, while others do not significantly affect the duration and even quality of life. The most severe forms of hereditary fetal pathology cause spontaneous termination of pregnancy or are accompanied by stillbirth.

Thanks to the success of the development of medicine, about a thousand hereditary diseases today can be detected even before the birth of a child using prenatal diagnostic methods. The latter include ultrasound and biochemical screening of the I (10-14 weeks) and II (16-20 weeks) trimesters, which are carried out to all pregnant women without exception. In addition, if there are additional indications, it may be recommended to undergo invasive procedures: chorionic villus biopsies, amniocentesis, cordocentesis. If the fact of severe hereditary pathology is reliably established, a woman is offered an artificial termination of pregnancy for medical reasons.

All newborns in the first days of their life are also subject to examination for hereditary and congenital metabolic diseases (phenylketonuria, adrenogenital syndrome, congenital adrenal hyperplasia, galactosemia, cystic fibrosis). Other hereditary diseases that are not recognized before or immediately after the birth of a child can be detected using cytogenetic, molecular genetic, biochemical research methods.

Unfortunately, a complete cure of hereditary diseases is currently not possible. Meanwhile, with some forms of genetic pathology, a significant prolongation of life and ensuring its acceptable quality can be achieved. Pathogenetic and symptomatic therapy is used in the treatment of hereditary diseases. The pathogenetic approach to treatment involves substitution therapy (for example, blood clotting factors in hemophilia), limiting the use of certain substrates in phenylketonuria, galactosemia, maple syrup disease, filling in the deficiency of a missing enzyme or hormone, etc. Symptomatic therapy includes the use of a wide range of medications, physiotherapy, rehabilitation courses (massage, exercise therapy). Many patients with genetic pathology from early childhood need correctional and developmental classes with a speech pathologist and speech therapist.

The possibilities of surgical treatment of hereditary diseases are mainly reduced to the elimination of severe malformations that interfere with the normal functioning of the body (for example, correction of congenital heart defects, non-infection of the upper lip and palate, hypospadias, etc.). Gene therapy of hereditary diseases is still rather experimental in nature and is still far from being widely used in practical medicine.

The main direction of prevention of hereditary diseases is medical and genetic counseling. Experienced geneticists will consult a married couple, predict the risk of offspring with hereditary pathology, and provide professional assistance in making a decision about childbirth.