a new form of medical care, based on advances in medical and human genetics and emphasizing the preventive aspect of modern health care.
Medicogenetic consultation entails the registration of persons with hereditary diseases, the clinical observation of patients and their families, and genetic advice (for example, explaining to the parents and relatives of a patient or to the patient himself the risk of manifestation of a particular hereditary disease in his family). The work of S. N. Davidenko laid the scientific foundation for medicogenetic consultation in the USSR.
Medicogenetic consultation is equipped to offer advice and help to several categories of patients, including those in whom a hereditary disease or disorder associated with the mutation of one or two allelic genes. About 1,500 such diseases, including about 400 metabolic anomalies, are now known. Medicogenetic consultation can be helpful to patients in whom the hereditary disease is associated with a change in karyotype (the number and structure of the chromosomes). These patients have chromosomal disorders, such as Down’s, Klinefelter’s, and Shereshevskii-Turner’s syndromes. In addition, medicogenetic consultation benefits patients in whom the hereditary disease is associated with polygenic inheritance and is manifested under unfavorable environmental conditions (pylorostenosis, hypertension, and some forms of obesity) and parents who already have a child with a congenital defect and wish to know their risk of having another child with the condition. Married couples who are blood relations and healthy persons who are concerned about the possibility of the occurrence of a hereditary disease because of its presence in relatives may also take advantage of medicogenetic consultation.
Thus, the preventive side of medicogenetic consultation involves acquainting parents with the risk of hereditary diseases occurring in their offspring and recommending that relatives or latent (heterozygous) carriers of a mutant gene not marry. Medicogenetic consultation also provides clinical genetic information to obstetricians, internists, and pediatricians for the early diagnosis and prompt treatment of hereditary diseases
Advice to a patient is of limited value if the hereditary disease is not accurately diagnosed, if its characteristics in a given family are not noted, if acquired diseases masked by hereditary diseases (phenocopies) are not ruled out, and, in the case of recessive hereditary diseases, if the latent (heterozygous) carrier of a mutant gene is not identified. Careful genealogical analysis of the family is very important, since it often helps to determine the type of disease inherited. Relatives with similar or different hereditary diseases, the age at which the disease is most often manifested, the family’s ethnic background, the frequency of marriages between relatives, and premature births, abortions, miscarriages, and stillbirths are recorded in the family case history file.
Hereditary diseases are divided into three groups, according to the likelihood of recurrence in a family. The first category consists of diseases with a high degree of genetic risk (1:4), including those with autosomal-dominant, autosomal-recessive, and sex-linked inheritance. The second consists of diseases with a moderate degree of genetic risk (less than 1:10), including those caused by fresh mutations and chromosomal diseases; diseases with a polygenic type of inheritance (that is, a substantial number of congenital anomalies); and hereditary diseases that develop against a genetically unfavorable background. The third category includes diseases with little or no risk of recurrence.
Medicogenetic consultation requires the resolution of a number of ethical and legal problems. In the opinion of most clinical geneticists, the function of the consultation should be limited to advice and indication of the degree of risk that a hereditary disease or disorder will occur in offspring. However, some believe that medicogenetic consultation should give directives instead of advice. According to the recommendation of a group of World Health Organization experts (1969), the goal of the medicogenetic consultation should be not the well-being of future generations but the welfare of those who seek advice. The preventive emphasis of Soviet medicine mandates the registration of families with a high risk of hereditary disease, so that the possibility of its developing in future generations can be anticipated. The medicogenetic consultation follows the same principle as the regular medical checkup: patients are put in special hospitals or clinics only for examination or in cases where diseases become aggravated.
REFERENCESStevenson, A., and B. Davison. Mediko-geneticheskoe konsul’tirovanie. Moscow, 1972. (Translated from English.)
Harris, G. Osnovy biokhimicheskoi genetiki cheloveka. Moscow, 1973. (Translated from English.)
IU. E. VEL’TISHCHEV and IU. I. BARASHNEV