A new small supernumerary marker chromosome involving 14pter → q12 in a child with severe neurodevelopmental retardation: case report and literature review.

Unstable, gene-rich pericentric regions have been associated with various structural aberrations including small supernumerary marker chromosomes (sSMCs). We hereby report on a new sSMC derived from chromosome 14, generating trisomy 14pter → q12 in a child with severe neurodevelopmental delay. The patient featured facial dysmorphism, generalized hypotonia, transverse palmar creases, structural brain abnormality, and severe cognitive and motor impairment. Literature review indicated this to be a unique case of sSMC 14 which was only composed of pter → q12, and the phenotype secondary to duplications of the similar region partially overlaps with the phenotype reported in this study. The genetic analysis on our case helps to better delineate karyotype-phenotype correlations between proximal trisomy 14 and associated clinical phenomena, and we also propose that the involved chromosomal regions may contain dosage-sensitive genes which are important for the development.