A non-mosaic isodicentric Y chromosome resulting from breakage and fusion at the Yq pseudo-autosomal region in a fetus.

The dicentric Y chromosomes are the most commonly found in the structural aberration of Y chromosome. If the dicentric chromosome has completely symmetric arms, it is considered an isodicentric chromosome. The sites of breakage and fusion at Yp and Yq are variable, but breakage and fusion at the pseudo-autosomal region has never been reported. Herein we reported identification de novo isodicentric (Yq12) in a fetus. The fusion occurred at Yq pseudo-autosomal region very close the telomere and resulted in duplication of Y chromosome. The baby was grossly normal at birth. In conclusion, isodicentric Y chromosome could result from breakage and fusion at the Yq pseudo-autosomal region.