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

• We described a patient, with a de novo sSMC involving 14 pter → q12.
• This is the first case of sSMC 14 which is only composed of pter → q12.
• Decreased cerebellar volume is a novel phenotype found in sSMC 14.
• Our case helps to delineate karyotype–phenotype correlations of partial trisomy 14.

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.