De novo origin of multiple small supernumerary marker chromosomes (sSMCs) in a child with intellectual disability and dysmorphic features

Small supernumerary marker chromosomes (sSMCs) are a heterogeneous group with regards to their clinical effects as well as their chromosomal origin and their shape. The sSMCs are associated with mental retardation and dysmorphic features. Multiple sSMCs are rarely reported. We report four sSMCs in a case of dysmorphic features and intellectual disabilities. Among the four sSMCs, one sSMC confirmed to be chromosome 5 derived sSMC using fluorescence in situ hybridization (FISH) and spectral karyotyping (SKY). The sSMCs were de novo originated as parental chromosomal analysis revealed normal karyotypes. The sSMC derived from chromosome 5 might be associated with mental retardation and dysmorphic features in the present case. However the remaining three sSMCs might have originated from repetitive sequences of chromosomes.