Rare Constitutional Chromosomal Rearrangements Found In ThreeProbands

Complex chromosomal rearrangements (CCRs) are characterized as rare reciprocal exchanges between three or more chromosomes with at least three breakpoints. Apparently balanced CCRs can be associated with mental retardation and congenital abnormalities. In some cases these abnormalities can be caused by submicroscopic deletions or duplications which is possible to detect by high resolution molecular cytogenetic methods. In our work we present clinical, cytogenetic and molecular cytogenetic findings of three patients with rare constitutional chromosomal rearrangements. Two of them can be included in group CCRs, the third patient has an unusual chromosomal exchange which involves three chromosomes, but only two breakpoints. This rearrangement was not reciprocal and simulated a simple reciprocal translocation t(7;18) on G-banded chromosomes. For precise identification of these chromosomal rearrangements we used G-banding, SKY, FISH, CGH, HR-CGH and oligonucleotide based array-CGH techniques. Proband 1 was a 7-year-old girl with stigmatisation, mental retardation and autism. We detected apparently balanced karyotype 46,XX,der(2)t(2;5),der(5)t(2;5;10),der(10)t(2;10)de novo. Proband 2 was a newborn stigmatised boy, we revealed familiar apparently balanced karyotype with double two way translocation 46,XY,t(1;14)(p34;q24),t(4;6)(q25;p23)pat. Proband 3 was a newborn boy without significant anomalies, growth retardation was developed later. Karyotype of this patient was 46,XY,der(7)t(6;7)(q25.3;q21.2),der(18)t(7;18)(q21.2;q22.3)del( 18)(q23?-qter)de novo. We conclude that it is necessary to use all available classical and molecular cytogenetic methods for clarification of complex and unusual chromosomal exchages and verification of suspect imbalances.