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Created in 1987, the department of medical genetics finds its origins in molecular endocrinology research which had developed from the seventies at the Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM) of the Faculty of Medicine. After its fusion with the Center of Human Genetics of the ULB, in 1992, the department is composed of three units: the lab of molecular genetics and oncology, the lab of cytogenetics and a clinical genetics unit. One thousand consultations of genetic counseling and more than 15,000 molecular or cytogenetic diagnostic procedures are performed annually. The development of the clinical activities was paralleled by a very active research activity, resulting in a series of "firsts". Amongst the main results are: the identification of the first mutations responsible for congenital hypothyroidism; the molecular cloning of the TSH receptor and of a series of "orphan" G protein-coupled receptors; the identification of a novel neuropeptide, nociceptin, by the first example of "reverse pharmacology"; the identification of olfactory receptors on the sperm of mammals, including man; the identification in molecular terms of the mechanisms responsible for acquired and hereditary hyperthyroidisms; the identification of the chemokine receptor CCR5 as the major coreceptor of HIV-1, and of the prevalent mutation of CCR5 conferring resistance to HIV to about 1% of the European population.

In the literature dealing with the impact of genetic counsel in the reproduction decision, two aspects are discussed: 1. memorization and appraisal of the recurrence risk, chosen options for family planning, appraisal of genetic counsel by the patients 2. mechanisms of decision making and psychological impact of genetic counsel.

1000 cases of genetic counseling have been reviewed. Most patients are sent to the genetic center by gynecologists (68.4%), mostly because of a personal or previous familial history (64%). This previous history concerns mainly congenital malformations (44%, 283/640) and mental retardation (24%, 154/640). Generally, the patients consult outside a pregnancy, nevertheless one fourth comes after conception and this occurs more often when the proband is a family member (38% versus 19% when the proband is a spouse and 20% when the proband is a child). Ten percent of the patients knowing they could be at risk because spouse or child is affected consult after having already had a child or having had another child. The mode of inheritance of the diseases for which patients with previous family history consult is as follows: mendelian inheritance (36%), multifactorial inheritance (19%), chromosomal defect (18%), non genetic (5%), variable inheritance (2%), unknown (15%) and insufficient information (5%). The majority of patients coming for previous familial history could be tranquilized, the recurrence risk was either small or minimal. In 2.6% of the cases, a high recurrence risk has been given and the risk could not be evaluated in 7% of the cases. The importance of genetic counseling is stressed by the fact that antenatal diagnosis could be proposed to half of the patients with a recurrence risk equal or higher than 1%.

The authors report the results of chromosomal analyses performed on 6235 amniocenteses and 559 choriocenteses. Whereas the frequencies of chromosomal anomalies observed respectively on amniocenteses and choriocenteses did not differ significantly, the comparison of the types of aberrations found revealed, in chorion villi, a relatively high proportion of lethal anomalies, never encountered in amniocyte cultures. Furthermore, chromosomal mosaicism was observed 10 times more frequently on chorion villi than on amniotic cells. These results are globally comparable to those reported in other surveys. In view of literature reports of discordances between fetal chorionic karyotypes, never found in amniocenteses, rapid karyotyping from chorion villi is not as reliable as from amniotic cells. Taking into account the risk of cytogenetic discordance specific to choriocentesis, it is recommended that this method be strictly limited to pregnancies with high genetic risk.