CHROMOSOMAL DISEASES IN THE HUMAN PATHOLOGY

Background. Chromosomal diseases are the cause of 45-50 % of multiple birth defects. Basic research on mutations is performed using genomic technologies to identify a correlation between genotype and phenotype in aneuploidies and to understand its pathogenesis. Objective. The aim of the research is to study the etiology, pathogenesis of symptoms and diagnostics for patients with Down, Klinefelter, Turner syndromes and double aneuploidies by 21 and sex chromosomes. Methods. A literature review by the keywords “Down syndrome”, “Klinefelter syndrome”, “Turner syndrome”, “double aneuploidy” for the period of 2000-2020 was carried out. Results. Down, Klinefelter and Turner syndromes are the most common aneuploidy among viable newborns. Frequency of meiotic non-disjunction events causing these aneuploidies increases with the age of a woman. Identified genes are responsible for pathogenesis of symptoms in trisomy 21, Turner and Klinefelter syndromes. Diagnostics of chromosomal diseases includes prenatal screening programs and postnatal testing. Conclusions. Cytogenetic variants of Down syndrome are simple complete trisomy 21, translocation form and mosaicism. Trisomy 21 is associated with advanced maternal age. Phenotypic manifestations of Down syndrome are associated with the locus 21q22. The maternal and parental nondisjunction of X-chromosomes in meiosis causes Klinefelter and Turner syndromes. These chromosomal diseases are variants of intersexualism with intermediate chromosomal sex. Down-Klinefelter and Down-Turner syndromes are double aneuploidies. Patients have a Down syndrome phenotype at birth, and signs of Klinefelter and Turner syndromes occur during puberty. Diagnosis of aneuploidy is based on the cytogenetic investigation (karyotyping), DNA analysis, ultrasonography and biochemical markers of chromosomal pathology.