Characterization of a de novo sSMC 17 detected in a girl with developmental delay and dysmorphic features

Lana Stavber, Sara Bertok, Jernej Kovač, Marija Volk, Luca Lovrečić, Tadej Battelino, Tinka Hovnik

The majority of small supernumerary marker chromosome cases arise de novo and their frequency in newborns is 0.04%. We report on a girl with developmental delay and dysmorphic features with a non-mosaic de novo sSMC that originated from the pericentric region of q arm in chromosome 17. The girl presented with developmental delay, speech delay, myopia, mild muscle hypotonia, hypoplasia of orbicular muscle, poor concentration, and hyperactivity. Main dysmorphic features included: round face, microstomia, small chin, down-slanting palpebral fissures and small lobules of both ears. At present, her developmental abilities are still delayed for her chronological age but she is making evident progress with speech. A postnatal array comparative genomic hybridization showed a 2.31 Mb genomic gain indicating microduplication derived from pericentric regions q11.1 and q11.2 of chromosome 17. Additional conventional cytogenetic analysis from peripheral blood characterized the karyotype as 47,XX,+mar in a non-mosaic form. The location of microduplication was confirmed with fluorescence in situ hybridization. The proband's microduplication encompassed approximately 40 annotated genes, several of which have been associated with phenotypic characteristics of the proband. This is the first report of sSMC 17 including this particular chromosomal region in non-mosaic form.