Microdeletion of chromosome 22q11 is one of the common chromosomal abnormalities associated with inborn cardiac defects. The frequency of this microdeletion syndrome is very high. Its phenotype is associated with very serious feature (cardiac defects, in certain cases thymic aplasia, immunodeficiency, hypocalcemia, hypoparathy- roidism and cleft palate). The FISH (fluorescent in situ hybridization) method ensures reliable detection of microdeletion 22q11. According to results of our molecular cytogenetic studies microdeletion 22q11 was detected roughly in 30 % of patients with inborn cardiac defects and some other phenotypic signs. Most frequent cardiac defects associated with 22q11 microdeletion are tetralogy of Fallot and interrupted aortic arch. In two cases other chromosomal aberrations were found - mosaics 45,X/46,XY and 45,X/46,XX/47,Xder(X).

        Key words: inborn cardiac defects, Di George syndrome, microdeletion 22q11, CATCH-22, FISH, gonosomal aneuploidy