Endocrine Abstracts

Trisomy 18, or Edwards syndrome, is a chromosomal disorder, due to the presence of a supernumerary chromosome 18. Worldwide, it is estimated to have a prevalence of 1/6000 live births, of which the most affected are female. Infants with trisomy 18 have a high mortality rate, secondary to the lethal malformations associated with this syndrome. The objective of this study is to describe the clinical and cytogenetic characteristics of these patients and to demonstrate the value of genetic counseling. This is a cross-sectional descriptive study conducted over a period of 5 years, from July 2015 to April 2019, at the medical genetics department of the University Hospital of Ibn Rochd in Casablanca. Five patients with Edwards syndrome were admitted to the department, with a female predominance; 3 girls and 2 boys (sex ratio= 0.67). The mean age at diagnosis was 37.40 ± 23.98 days (9 days-2 months). Trisomy 18 was clinically suggested in two cases because of facial dysmorphia and malformative syndrome characteristic of the chromosomal anomaly, whereas two patients were hospitalized in an intensive care unit for decompensated heart failure due to congenital heart disease. Finally, one patient presented with respiratory distress in the newborn with a poly-malformative syndrome at the time of diagnosis. The karyotype performed confirmed the diagnosis of trisomy 18 free and homogeneous in all five patients, and genetic counseling was performed. Genetic counselling is a specialized preventive medicine consultation, which allows the risk of recurrence to be calculated for any chromosomal anomaly, including Edwards syndrome. Thus, for a couple with a child with free and homogeneous trisomy 18, the probability of recurrence in the next pregnancy is 1%. In cases where trisomy 18 is partial, and therefore secondary to a structural anomaly, it is necessary to perform a karyotype in the parents to eliminate carriers with a balanced translocation, because the probability of recurrence is greater. The incidence of trisomy18 also increases with advanced maternal age. Furthermore, the complexity and severity of the clinical picture and the high rate of neonatal and infant mortality emphasize the importance of prenatal diagnosis of this disease.

Keywords: trisomy18, facial dysmorphia, prenatal diagnosis.