SOMATIC MOSAICISM IN PATIENTS WITH R (18) AND CONGENITAL HEART DISORDER
Syndrome r (18) - ring 18 chromosome cytogenetically is characterized by a complete or mosaic forms a ring chromosome 18 with the absence of the distal portions of the long and short arm of the chromosome. The clinical picture includes multiple dysmorphia, combined with varying degrees of mental retardation. Committal involvement of cardiovascular system and congenital heart defects typically are not described in cases of r (18). We observed 18-year-old patient with mental retardation, multiple facial dysmorphia, and subaortic stenosis. During standard karyotyping by PHA-stimulated lymphocytes patient revealed 46, XY, r (18) karyotype. Since congenital heart defects are not common feature of r (18) we hypothesized mosaic chromosomal aberrations and performed additional FISH analysis on blood smears using Aneu Vision (CEP 18) and To Tell Mix 11, Mix 12 probes. The study revealed three signals of chromosome 18 centromere and subtelomeric deletion of chromosome 18 in 15 % of the cells, contained two signals from the centromere of chromosome 18 with subtelomeric deletion to form a ring in 80 % of cells, 5 % of the uncultured cells in blood smear contained two signals from the centromere of chromosome 18 without subtelomeric deletion. In conclusion we describe clinical case of somatic mosaicism in patients with r (18) in combination with 18 trisomy in 15 % of blood cells, leading to combined phenotype of mental retardation and congenital heart defect.