“…According to the pathogenesis of chromosomal aberrations, isolated trisomy 18p can be divided into four types: unbalanced translocation, small supernumerary marker chromosomes (sSMCs), 18p deletion, and isochromosome 18p duplication. Thirty-six cases of isolated trisomy 18p have been published in the literature [ 15 – 18 ], and the clinical phenotypes of most cases were intellectual disability, developmental delay, distinct facial features, epilepsy syndromes, and short stature. Seven of these cases were phenotypically normal.…”