engleski

Rare unbalanced translocation involving chromosome 15 and 18 in a patient with monosomy 18p

In this study we performed clinical and cytogenetic investigation in an additional case of monosomy 18p due to rare unbalanced translocation. Our patient is an 8-year-old girl with mild developmental delay and dysmorphic features. Cytogenetic analyses were performed on slides obtained by peripheral blood culture. High-resolution GTZG-, RBG- and CBG-methods were used for chromosome identification. FISH method with whole chromosome 15 and 18 painting probes, D15Z1, SNRPN, PML, D18Z1 and D18S552 probes were used for precise characterization of structural rearrangement. Analysis revealed monosomy 18p resulting from an unbalanced whole arm translocation (WAT) between chromosome 15 and 18. Aberrant chromosome presents two centromeric constrictions. CBG-banding did not show two separate centromeric regions, while FISH analysis confirmed the presence of centromeric regions from chromosome 15 and 18 on the derived chromosome. Breakpoints were attributed to 15p11.2 and 18p11 bands. Parental karyotype were normal indicating de novo origin of chromosome rerrangement. WAT are rare constitutional abnormalities. Aberration results from centromeric fission or juxtacentromeric break and reciprocal exchange of entire arms of two chromosomes. WAT involving chromosome 18 account for approximately 16% of all cases of monosomy 18p. To the best of our knowledge only three cases of t(15 ; 18) leading to 18p monosomy have been reported so far. This study adds new evidence that translocation is not the results of α -satellite DNA recombination, and that other factors (low-copy repeats, segmental duplications) may be important in the etiology of WAT (15 ; 18) in our patient as well as in two other cases reported so far.

Translocation; chromosomes 15 and 18

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