The First Case of a Small Supernumerary Marker Chromosome 18 in a Klinefelter Fetus: A Case Report

Document Type: Case Report(s)

Authors

1 Medical Biotechnology Department, School of Advanced Medical Sciences and Technology, Shiraz University of Medical Sciences, Shiraz, Iran

2 Department of Medical Genetics, School of Medical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran; and Transgenic Technology Research center, Shiraz University of Medical Sciences, Shiraz, Iran; and Comprehensive Medical Genetic Center, Shiraz University of Medical Sciences, Shiraz, Iran

3 Diagnostic Laboratory Sciences and Technology Research Center, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran

4 Comprehensive Medical Genetic Center, Shiraz University of Medical Sciences, Shiraz, Iran

5 Department of Medical Genetics, School of Medical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran; and Comprehensive Medical Genetic Center, Shiraz University of Medical Sciences, Shiraz, Iran; and Department of Psychiatry, University of Miami Miller School of Medicine, Miami, FL 33136, USA

Abstract

Small supernumerary marker chromosomes (sSMCs), or markers, are abnormal chromosomal fragments that can be hereditary or de novo. Despite the importance of sSMCs diagnosis, de novo sSMCs are rarely detected during the prenatal diagnosis process. Usually, prenatally diagnosed de novo sSMCs cannot be correlated with a particular phenotype without knowing their chromosomal origin and content; therefore, molecular cytogenetic techniques are applied to achieve this goal. The present study aimed to characterize an sSMC in a case of Klinefelter syndrome using an in-house microsatellite analysis method and fluorescent in situ hybridization (FISH) technique. Amniotic fluid was collected from a pregnant woman who was considered to have risk factors for trisomy higher than the screening cut-off. Karyotype analysis was followed by the amplification of different microsatellite loci and FISH technique. Karyotype analysis identified a fetus with an extra X chromosome and also an sSMC with unknown identity. Further investigation of the parents showed that the sSMC is de novo. Microsatellite amplification by quantitative fluorescent PCR (QF-PCR) and FISH analysis showed that the sSMC is a derivative of chromosome 18. Eventually, the patient decided to terminate the pregnancy. Here, the first case of the coincidence of sSMC 18 in a Klinefelter fetus is reported.

Keywords