Mechanism of development and classification
Genetic diseases of somatic cells represent a recently identified group within the structure of hereditary pathology. The main feature of these disorders is that genetic changes affect exclusively somatic cells of the body rather than germ cells.
- Etiology: the pathological process is based on the emergence of specific chromosomal rearrangements. These changes are identified in malignant neoplasms.
- Pathogenesis: the primary mechanism of tumor development is oncogene activation, which occurs as a direct consequence of the aforementioned chromosomal rearrangements.
Clinical examples
In clinical practice, a number of malignant neoplasms are distinguished whose development is directly associated with somatic chromosomal aberrations. The most characteristic examples of this group of diseases include:
- Retinoblastoma.
- Wilms' tumor (also known in medical literature as nephroblastoma).
Diseases with genetic incompatibility between mother and fetus
A separate yet closely genetics-related category consists of diseases developing due to genetic incompatibility between a pregnant woman and the fetus.
The main cause of their occurrence is an immunological reaction of the maternal organism to specific antigens of the developing fetus. The most typical and thoroughly studied disease in this group is hemolytic disease of the newborn (HDN).
Types of immunological conflicts in HDN
Hemolytic disease of the newborn can proceed in several scenarios depending on the type of antigens that triggered the immune reaction.
Rh incompatibility (rhesus factor):
- The mother is rhesus-negative (Rh-).
- The fetus is rhesus-positive (Rh+). The fetus inherited its rhesus-positive allele from the father.
ABO incompatibility:
- Develops as an immunological conflict regarding blood group antigens of the ABO system.
- This type of incompatibility is also encountered in practice, although it has specific clinical course features compared to rhesus incompatibility.
Briefly: answers to topical questions
What specific chromosomal rearrangements underlie the development of retinoblastoma?
Sources indicate the following specific chromosomal rearrangement for retinoblastoma:
- Retinoblastoma — involved region: del 13q (14).
Retinoblastoma is listed among microcytogenetic syndromes caused by deletions or duplications of small chromosomal regions. The disease is a malignant tumor of the retina; it is frequently congenital, manifests within the first 3 months of life, and the peak number of cases is diagnosed under the age of 4 years.
Which gene is damaged during the development of Wilms' tumor (nephroblastoma)?
During the development of Wilms' tumor (nephroblastoma), the WT1 (Wilm's tumor-associated gene 1) is damaged. This autosomal gene is localized on the short arm of chromosome 11. Its mutations lead to developmental anomalies of the kidneys and genital organs. The disease can also develop as part of a microcytogenetic syndrome.
- Aniridia-Wilms' tumor syndrome — caused by a rearrangement of the del 11p (13) region. Characterized by absence of the iris, craniofacial anomalies, and the development of nephroblastoma in 1/3 of patients.
Through which blood antigen systems can hemolytic disease of the newborn develop?
Hemolytic disease of the newborn develops due to an immunological conflict between the mother and fetus owing to incompatibility in erythrocyte antigens.
- Rh system — conflict arises if the mother is Rh-negative and the fetus is Rh-positive. The D antigen is of primary importance.
- ABO system — an immunological conflict regarding ABO blood group antigens is possible.
Both variants are associated with the maternal immunological reaction to fetal antigens.
Which classes of maternal antibodies cross the placenta in hemolytic disease of the newborn?
In hemolytic disease of the newborn, maternal class G immunoglobulins (IgG) cross the placenta. During re-immunization (subsequent pregnancies), a large amount of IgG antibodies is produced, particularly of the IgG3 subclass directed against the D antigen. They easily cross the placental barrier, causing agglutination and hemolysis of fetal erythrocytes. In contrast, IgM class antibodies, which are formed at the beginning of the immune response, virtually do not cross the placenta.
To memorize examples of somatic mutations, use the mnemonic «RW»: Retinoblastoma, Wilms' tumor.
Class and exam questions
What underlies the pathogenesis of somatic cell diseases?
The main link in pathogenesis is oncogene activation, which occurs as a result of specific chromosomal rearrangements in the cell.
Which tumors are typical examples of this group?
Classic examples include retinoblastoma and nephroblastoma (Wilms' tumor).
Why does genetic incompatibility occur during pregnancy?
It develops due to the immunological reaction of the mother's organism to specific fetal antigens recognized as foreign.
What are the mandatory conditions for the development of rhesus incompatibility?
The conflict arises when the pregnant woman is Rh-negative, and the fetus has inherited an Rh-positive allele from the father.
What else to study on this topic
- Molecular mechanisms of oncogene activation in chromosomal rearrangements
- Clinical features and diagnosis of retinoblastoma
- Specifics of the clinical picture of nephroblastoma (Wilms' tumor)
- Distinctive clinical features of ABO incompatibility compared to Rh incompatibility
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