There are two aspects to genetic counseling: the estimate of the genetic risk and the humane presentation of the risk to the patient, taking into consideration all the social and psychologic implications of the probability estimate. Most of those who seek advice from a genetic counseling clinic suffer from predominantly non genetic disorders.
The taking of careful family history is mandatory, and an accurate clinical diagnosis, based on personal examination of the patient, is a prerequisite. The pedigree should include parents, sibs, uncles and aunts, grandparents, and cousins. Specific inquiry concerning the possible existence of consanguinity should be made. An increased consanguinity among the parents of, individuals affected with a recessive disease is frequently observed.
When a careful family history discloses that a condition is inherited in a clear-cut dominant, recessive, or X-linked fashion, the genetic risk for subsequent offspring, given one affected, can be calculated. Frequently, however, genetic counseling has to rely on approximate “empiric risk figures,” which are continually changing as heterogeneous conditions are separated into discrete homogeneous entities. In some recessive diseases it is possible to recognize the healthy career of the abnormal gene by appropriate biochemical or tissue culture techniques. Requests for counseling are common in clinical medicine; unfortunately, the information upon which to base a helpful opinion is frequently lacking.
New diagnostic techniques such as karyotype analysis provide some insight into risks for chromosomal disease. Mongolism may be used as an example. With a negative family history, the empiric risk of mongolism is 1/650. If the mother is age 25, the risk is 1/2000, but at age 45 it is increased to 1/50. If the parents have had one mongol child, their risk of recurrence is about 1 to 2 per cent and independent of maternal age.
Chromosome studies of the parents will sharpen these predictions. If the mother carries a 14:21 translocation, the odds are about 1 in 3, but if.the father is the translocation heterozygote, the odds drop below 1 in 20. If amniocentesis is performed during pregnancy, then a karyotype gives the exact diagnosis on the fetus. The-physician and parents can then consider a therapeutic abortion. The ultimate aim in genetic counseling is to take the guesswork out of predictions and to be able to provide therapy for individuals with genetic afflictions.
