Types of hereditary diseases
Human hereditary diseases are those pathological conditions caused by a change in genetic material. If these changes occur in the elementary units of heredity, which are called genes, then monogenic or Mendelian hereditary diseases arise, namely, inherited by the rules, the discovery of which is attributed to Gregor Mendel.
As examples of monogenic hereditary diseases, diseases such as achondroplasia, in which skeletal damage occurs, family polycystic kidney disease, congenital cataracts, Marfan syndrome( lesion of the skeleton, heart, eye), hereditary pancreatitis, cystic fibrosis( systemic damage manifested asusually, chronic obstructive bronchopulmonary process and disruption of the gastrointestinal tract), phenylketonuria, manifested by mental retardation and mental disorders, adenomacolonic polyposis, hemophilia.
If changes affect the chromosomes in which almost all genes are located and lead to a change in the number or structure of chromosomes, then chromosomal diseases occur. Well-known examples of chromosomal diseases are the syndromes of Down, Edwards, Turner, "cat's scream."
If changes occur in mitochondrial DNA, then this leads to mitochondrial diseases. Examples are optic atrophy, external ophthalmoplegia, mitochondrial myopathies, myoclonus-epilepsy syndromes and torn red muscle fibers. Most monogenic hereditary diseases are rare.
In addition, hereditary diseases are also attributed to such diseases, in the development of which, apparently, equally important are both genes and environmental factors. They are called multifactorial diseases, as they depend on the action of a large number of factors, both genetic and external, and include all chronic non-infectious diseases, such as diabetes, atherosclerosis, bronchial asthma, and isolated congenital malformations. The incidence of these diseases in the population is very high. Suffice it to recall that atherosclerosis and coronary heart disease are at the top of the list as the cause of death. In addition, it is customary to distinguish between diseases caused by the action of predominantly external factors. These include injuries, frequent infectious diseases, which affect almost everyone. However, many researchers believe that the occurrence of these diseases also depends on the genetic constitution, albeit to a small extent. It is known that even during epidemics a part of the population does not fall ill, having a genetically conditioned immunity to the corresponding infection.
An actual example of modern medicine is AIDS.It has been established that in individuals with a particular form of one of the genes( the chemokine receptor gene), susceptibility to the acquired immunodeficiency virus is reduced. Such a classification of the whole human pathology into separate groups, depending on the significance of hereditary factors in the etiology and pathogenesis of human diseases, is undoubtedly one of the important achievements of medical genetics.