Down Syndrome and Other Common Chromosomal Abnormalities in Humans with Recent Advances in Cytogenetic Diagnosis

Chromosomal abnormalities constitute a major cause of congenital anomalies, intellectual disability, infertility, recurrent pregnancy loss, developmental delay, and various genetic syndromes in humans. These abnormalities may involve numerical changes, such as aneuploidy, or structural alterations including deletions, duplications, translocations, inversions, and ring chromosomes. Among them, Down syndrome remains the most prevalent autosomal chromosomal disorder worldwide, resulting from the presence of an additional copy of chromosome 21. Significant advances in cytogenetic and molecular cytogenetic technologies over recent decades have transformed the diagnosis, characterization, and clinical management of chromosomal disorders. Conventional karyotyping continues to serve as the standard method for detecting large chromosomal abnormalities, while fluorescence in situ hybridization (FISH), chromosomal microarray analysis (CMA), quantitative fluorescence polymerase chain reaction (QF-PCR), multiplex ligation-dependent probe amplification (MLPA), and next-generation sequencing (NGS)-based techniques have substantially improved diagnostic accuracy and resolution. Early prenatal diagnosis, genetic counseling, and personalized clinical management have enhanced healthcare outcomes for affected individuals and their families. This review summarizes the epidemiology, genetic basis, clinical manifestations, classification, and diagnosis of Down syndrome and other common chromosomal abnormalities, with particular emphasis on recent advances in cytogenetic diagnostic technologies and future prospects for precision genomic medicine.