Molecular cytogenetic characterization of partial monosomy 2p and trisomy 16q in a newborn: A case report

Abstract

Trisomy 16q is a rare disorder with severe abnormalities, which always leads to early postnatal mortality. It usually results from a parental translocation, exhibiting 16q duplication associated with another chromosomal deletion. The present study reports on the clinical presentation and molecular cytogenetic results of a small-for-gestational-age infant, consisting of partial trisomy 16q21→qter and monosomy 2p25.3→pter. The proband presented with moderately low birthweight, small anterior fontanelles, prominent forehead, low hairline, telecanthus, flat nasal bridge, choanal atresia, clinodactyly of the fifth fingers, urogenital anomalies, congenital muscular torticollis and congenital laryngomalacia. The last two traits have not previously been reported in any trisomy 16q and monosomy 2p cases. The proband was trisomic for the 16q21→qter chromosomal region with the karyotype 46,XY,der(2)t(2;16)(p25;q21)pat. The chromosomal anomaly was the result of unbalanced segregation of a paternal balanced translocation, 46,XY,t(2;16)(p25;q21). In this case, molecular cytogenetic analysis had a critical role in delineating the proband's clinical phenotype. Although this patient had a 16q21→qter duplication and a 2p25.3→pter deletion, the latter may have had mild phenotypic effects when associated with trisomy 16q. The literature was also reviewed, focusing on cases with the same breakpoints, localizations and clinical features reported in recent years.

Keywords: 16q trisomy; 2p monosomy; case report; molecular cytogenetic diagnosis; unbalanced segregation of a paternal balanced translocation.

Figure 1.

The Affymetrix CytoScan HD arrays depicted (A) a1.4 Mb deletion in the short arm of chromosome 2 located at 2p25.3 to 2pter, presented in red, and (B) a 30.2 Mb duplication in the long arm of chromosome 16 located at 16q21 to 16qter, presented in blue.

Figure 2.

Karyograms of the proband and the proband's father. (A) Karyogram of the proband with the karyotype 46,XY,der(2)t(2;16)(p25;q21)pat. (B) Karyogram of the proband's father with the karyotype 46,XY,t(2;16)(p25;q21).