Prenatal diagnosis of two different unbalanced forms of an inherited (Y;12) translocation.

The identification of an unexpected structural chromosome rearrangement at prenatal diagnosis can be problematic and raises unique genetic counseling issues. We describe two consecutive prenatal cases within a family with an inherited unbalanced (Y;12) translocation and discuss the genotype-phenotype correlation. The first fetus presented with 12qter monosomy and pseudoautosomal region 2 trisomy, while the second fetus had the alternative unbalanced state. Although the first fetus had a structural heart defect, such small imbalances might not give sonographic findings, making their prenatal diagnosis difficult. However, congenital abnormalities are expected in both unbalanced forms of the translocation, including mental retardation, which could be explained by the gene dosage variation of P2RX2. To our knowledge, these are the first published cases reporting this subtype of (Y;12) translocation, in both balanced and unbalanced states.