Small supernumerary marker chromosome and chromosome 18p abnormalities / 中华实用儿科临床杂志

ABSTRACT

Humans typically have 22 pairs of autosomal chromosomes in cells,and a pair of sex chromosomes.Some individuals have an extra,autosomal chromosome called a small supernumerary marker chromosome (sSMC).sSMC is a structurally abnormal chromosome fragment.The fragments are too small and no-specific banding pattern to be identified by conventional banding cytogenetic analysis.Array-based comparative genomic hybridization (aCGH),fluorescence in situ hybridization (FISH) or other molecular biological methods are necessary for the diagnosis.This article summarized the karyotype,pathogenesis,and the clinical manifestations of the sSMC-related chromosome 18p abnormalities.The patients with sSMC usually presented with abnormal chromosome syndrome.Some syndromes are relative common,such as Pallister-Killian syndrome,isochromosome 18p syndrome,Cat eye syndromes or Emanuel syndrome.sSMC is considered to be the frequent cause of mental retardation.The patients have no specific symptoms.With the progress of molecular cytogenetics,more sSMC has been identified.Genetic counseling and prenatal diagnosis are important to prevent sSMC.Molecular cytogenetic techniques are necessary to the diagnosis.