Unbalanced translocations involving chromosome region 10q25.3q26.3 in patients with intellectual disability and complex phenotypes.

We describe 2 Ukrainian families with unbalanced reciprocal translocations (RTs) involving the distal part of chromosome 10q. In both families, the fathers were healthy carriers of the RT. Two affected patients from the first family had an ∼2.3-Mb loss at 10q26.3 and an ∼25-Mb gain at 2q35qter, and the patient from the other family had an ∼12.5-Mb loss at 5p15.2pter and an ∼18-Mb gain at 10q25.3q26.3. We assume that intellectual disability (ID) in association with congenital anomalies observed in our patients was the result of the cumulative effect of both gains and losses of the chromosomal regions involved in each translocation. Comparison of the sizes of the deleted and duplicated segments in our families as well as in other published families with translocations affecting the distal part of 10q showed that generally deletions seem to be ∼2 times more harmful than duplications of the same size. The data obtained here may contribute to improve the diagnosis and genetic counseling of families with similar chromosomal imbalances.