[Molecular cytogenetic pre- and postnatal diagnosis of chromosomal abnormalities].

Molecular cytogenetic studies in the prenatal and postnatal identification of chromosomal anomalies in children with mental retardation and congenital developmental malformations are discussed. Molecular cytogenetic techniques, such as fluorescence in situ hybridization (FISH) are employed after the use of classic cytogenetic studies. FISH diagnosis is recommended to apply in the cases when classic cytogenetic methods are not beneficial: post- and prenatal autosomal trisomies; gonosomal aneuploidies, including mosaic forms; marker chromosomes; structural chromosomal anomalies, including fragile X syndrome. The authors' experience showed that (1) FISH should be utilized only as an adjunctive test for classical cytogenetic studies when banding techniques are ineffective; (2) FISH confirms a cytogenetic diagnosis; (3) multicolored probe detection gives an additional possibility in the FISH analysis. The findings demonstrate that molecular cytogenetic methods provide a rapid accurate approach to investigating and diagnosing chromosomal anomalies. Molecular cytogenetic diagnosis allows a more correct correlation of chromosomal abnormalities to be shown with a clinical picture and assists in identifying new chromosomal syndromes in children with undifferentiated forms of mental retardation and congenital malformations.