[Trisomy 18 or postnatal Edward´s syndrome: descriptive study conducted at the University Hospital Center of Casablanca and literature review].

Trisomy 18 is a chromosomal disease, caused by the presence of a supernumerary chromosome 18. Mortality among infants with trisomy 18 is high, secondary to lethal malformations associated with this syndrome. The purpose of this study was to describe the clinical and cytogenetic features of these patients, as well as the role of genetic counselling. We conducted a cross-sectional descriptive study over a 5-year period, from July 2015 to April 2019. The study involved, patients followed up in the Department of Medical Genetics at the University Hospital Center Ibn Rochd of Casablanca, having abnormalities suggestive of trisomy 18, then confirmed by cytogenetic study. The study enrolled 5 patients, 3 girls and 2 boys (female predominance; sex-ratio = 0,67) with clinically suspected Edward's syndrome, then confirmed by cytogenetic study. The mean age at diagnosis was 37.40 ± 23.98 days (9 days-2 months). Trisomy 18 was clinically suspected in two cases based on facial dysmorphism and malformative syndrome, a recognizable pattern of chromosomal abnormality. Two patients were hospitalized in the intensive care unit for decompensated heart failure associated with congenital heart disease, while one patient had neonatal respiratory distress associated with polymalformative syndrome at diagnosis. Cytogenetic study confirmed the diagnosis of free and homogeneous trisomy 18 in five patients, then genetic counselling was performed. The prevalence of trisomy 18 is variable. Global prevalence is estimated at 1/6000 live births, females are mostly affected. The diagnosis of trisomy 18 should be suspected at birth in newborns with typical craniofacial dysmorphism, arms lifted in supplication and permanent flexion of the fingers, the index finger overlapping the 3 finger, the little finger overlapping the 4 finger. There are several malformations associated with trisomy 18. This syndrome should be also suspected in the antenatal period in patients with abnormalities on obstetric ultrasound. Moreover, survival is low and only one in 10 newborns reach the first year of life.