Clinical and molecular findings in nine new cases of tetrasomy 18p syndrome: FISH and array CGH characterization

• Published in: Molecular cytogenetics Vol. 12; no. 1; pp. 5 - 7
• Main Authors: Slimani, Wafa, Ben Khelifa, Hela, Dimassi, Sarra, Chioukh, Fatma-Zohra, Jelloul, Afef, Kammoun, Molka, Hannachi, Hanene, Bouslah, Sarra, Jammali, Nesrine, Sanlaville, Damien, Saad, Ali, Mougou-Zerelli, Soumaya
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 08-02-2019; BioMed Central; BMC
• Subjects: Array CGH; Birth weight; Breakpoints; Cardiac patients; Care and treatment; Child & adolescent psychiatry; Chromosome 18; Chromosomes; Congenital heart defects; Copy number; Corpus callosum; Cytogenetics; Diagnosis; FISH; Fluorescence; Fluorescence in situ hybridization; Genetic aspects; Genetic disorders; Genomes; Genomics; Human genome; Hypoplasia; Hypospadias; Infertility; Intellectual disabilities; Low birth weight; Microcephaly; Microencephaly; Patients; Skin; Skin diseases; Small supernumerary chromosome marker; Strabismus; Supernumerary; Tetrasomy; Tetrasomy 18p; Tunisia; FISH; Tetrasomy 18p; Array CGH; Small supernumerary chromosome marker
• ISSN: 1755-8166; 1755-8166
• DOI: 10.1186/s13039-019-0414-8

Small Supernumerary Marker Chromosomes (sSMC) are rare chromosomal abnormalities, which have abnormal banding arrangement and take many shapes. Several disorders have been correlated with sSMC presence. The aim of this study is to characterize the sSMC derived from chromosome 18 by Fluorescence in situ hybridization (FISH) and Array Comparative Genomic Hybridization (aCGH).
Nine children with dysmorphic features have been investigated. They have these features in common: a triangular face, low-set ears, a large mouth with a thin upper lip, and a horizontal palpebral fissure. Epicanthus and strabismus were present in two patients. In addition, we have noticed microcephaly and mental and/or developmental delay with low birth weight. However, two patients had standard birth weight; one patient had hypospadias; two had skin problems; and three showed different congenital heart defects. One patient had corpus callosum hypoplasia. Systematic karyotype analysis revealed a de novo supernumerary chromosome. Array CGH showed a gain in copy number on the short arm of chromosome 18 in the nine cases. In one case, the sSMC seemed to be in mosaic. The breakpoints of the marker were identified using aCGH and FISH. Thus, the sSMC led to 18p tetrasomy with approximately 14 Mb lengths, between 364344 and 14763575 based on the human genome version 18.
These results have been completed by FISH in order to ascertain the shape of the sSMC. Our results confirm the uniqueness and particularity of the iso18p syndrome on the phenotypic as well as on the genetic level.