The monosomy 18p detected by the amniocentesis: de Grouchy syndrome 1

Abstract

Monosomy 18p (de Grouchy syndrome 1) is a structural chromosome aberration provoked by the deletion of a part of or the entire 18 chromosome's short arm. In 2/3 of cases it is provoked because of the de novo terminal deletion of 18 chromosome's short arm, while in the rest of the cases there is a transmission from parents. The clinical manifestations of this syndrome are moderate and nonspecific. In the clinical research they could be neglected. Its usual manifestations include: mental retardation in various degree, postnatal growth restriction, short stature, delayed speech development, as well as craniofacial malformations. At birth, the phenotypic manifestations of the syndrome are minimal and the abnormalities become visible after the age of three. The final diagnosis requires karyotyping and an analysis of fetal chromosomes or an analysis of an afflicted person. Previous research have shown that the critical point for the breakage located near the centromere in the region 18 p11.1 (it is present in 44% - 72% of examinees). The breakage in the region between p11.1 and p1.21 is linked to a higher degree of mental retardation compared to the breakages distally from these points at the p chromosome's arm. The examples of prenatally detected monosomy 18p are sporadic and they are usually found after abnormal ultrasound findings in the first trimester or accidentally by invasive prenatal diagnostics. In the cases of monosomy 18 p detected prenatally or in the cases of giving a birth to a child with this type of chromosomal aberration, a parents' karyotypes should be defined with the purpose to provide genetic advice to the parents.