Case report of a novel phenotype in 18q deletion syndrome

Abstract

The latest decades are characterized by an enormous progression in the field of human genetics. In consequences, for various phenotypic manifestations, genetic testing could identify a specific underlying cause. An estimated incidence for all types of 18q deletions is one in 55 000 births predominant on females. About 94% of cases with 18q deletion syndrome appearance are de novo , and the remaining 6% are the inherited from a parent carrying a balanced chromosomal translocation. We present the case of a 35-year-old female who was admitted in our Unit for a second ultrasound opinion after being diagnosed at the second trimester scan at gestational age of 21 weeks of pregnancy with multiple brain and heart malformations, having the recommendation for fetal magnetic resonance imaging (MRI). Further investigations included genetic analysis and pathological examination. Major malformations diagnosed and confirmed were agenesis of the corpus callosum , ventriculomegaly with dilated fourth ventricle, partial agenesis of vermis, bilateral anophthalmia with wide nasal base and left cleft lip. Additional, cardiac malformation, with an important ventricular septal defect and overriding aorta were noted. The results of the microarray analysis showed an abnormal fetal karyotype with a loss of 30.5 basis identified in the long arm of chromosome 18. Although most of the cases of 18q deletion are sporadically or de novo , could be cases where the possible existing syndromes can be inherited from a healthy or mild affected parent. Therefore, in order to establish the recurrence risk, parental karyotypes are recommended.

Prenatal diagnosis of chromosome 18 long arm deletion syndrome by high-throughput sequencing

“…Approximately 94% of children with 18q deletion are newly occurring chromosomal aberrations, and the other 6% are caused by unbalanced chromosomal translocation, as their parents are usually carriers of balanced chromosomal translocation. [ 2 ] The phenotype of 18q deletion syndrome varies greatly due to the location of chromosome breakage, the type of missing genes, and individual characteristics. However, at present, it is clear that most structural or numerical malformations resulting from deletions always produce significant adverse phenotypes.…”

“…Its clinical manifestations involve abnormal development of various systems, such as intelligence, face, movement, and so on. [ 2 – 5 ]…”

“…Chromosome 18 long arm deletion syndrome is a group of clinical syndromes caused by partial or total genetic material deletion on the long arm of chromosome 18 (18q), with a low incidence of approximately 1:40,000 [1] in neonates. Approximately 94% of children with 18q deletion are newly occurring chromosomal aberrations, and the other 6% are caused by unbalanced chromosomal translocation, as their parents are usually carriers of balanced chromosomal translocation [2] . The phenotype of 18q deletion syndrome varies greatly due to the location of chromosome breakage, the type of missing genes, and individual characteristics.…”

“…However, at present, it is clear that most structural or numerical malformations resulting from deletions always produce significant adverse phenotypes. Its clinical manifestations involve abnormal development of various systems, such as intelligence, face, movement, and so on [2–5] …”

“…Its clinical manifestations involve abnormal development of various systems, such as intelligence, face, movement, and so on. [2][3][4][5] Screening for structural or numerical abnormalities of chromosomes is usually carried out at 11 +0 to 13 +6 weeks of gestation and is used as an indispensable project of fetal routine examination in the second trimester of pregnancy to detect suspicious patients by ultrasound measurements or by combined test of serological indicator in early and second trimester of pregnancy. [6] Nevertheless, the results of these screenings are indirect methods that are affected by various factors such as gestational age, fetal posture, maternal body shape, amniotic fluid, and fetal movement.…”