OBJECTIVETo apply single nucleotide polymorphism (SNP) microarray for delineation of small supernumerary marker chromosome (sSMC) in two newborns.

METHODChromosome karyotyping was performed on newborns who were born in Jan. 2013 and Jan. 2014 in Haidian Maternal and Child Health Hospital because of the abnormalities found in pregnancy checkups. SNP microarray analysis was carried out on 2 newborns with de novo sSMCs (one was mos 47,XY, + mar[45]/46,XY[5] and the other was mos 47, XY, + mar [30]/46, XY [20]), which could not be determined by conventional banding techniques. Genomic DNA was extracted from cord blood samples, amplified, tagged and hybridized following the manufacturer' s protocol. Data were collected and analyzed.

RESULTThere was a 78. 6 Mb duplication in chromosome 8 for Newborn A, which was associated with 8p22 duplication syndrome; and a 32. 7 Mb duplication in chromosome 13 for Newborn B, which was not yet reported definitely as pathogenic. The newborn A was identified with agenesis of the corpus callosum, obvious right eyelid drooping, the onset of low muscle tone and mental developmental lag behind their peers, while the newborn B had normal findings on physical and mental evaluation.

CONCLUSIONSNP-array can identify sSMCs of newborns at the DNA level, and can be used as an important supplement to the conventional karyotype analysis, but the pathogenicity of positive outputs need further verification.