TETRASOMY-18P IN 2 CASES CONFIRMATION BY IN-SITU HYBRIDIZATION

Two cases with an extra small metacentric chromosome are described. Cl assic cytogenetic analysis was insufficient for identification of the marker origin. High resolution banding and fluorescence in situ hybrid ization (FISH) using a chromosome specific painting probe indicated th at both marker chromosomes originated from chromosome 18. The correlat ion between phenotype, cytogenetics and FISH results allowed us to con clude that the patients are tetrasomic for 18p. A comparison of the cl inical features of our two patients with other twelve previously repor ted patients where tetrasomy 18p was confirmed, is also presented.