Prenatal detection of an inverted X chromosome in a male.

An unusual case of an X chromosome with a pericentric inversion (p11.3q21.3) was detected prenatally in a male fetus. This inversion has not been previously characterized. Although the inverted chromosome was transmitted through the mother, no living males on the maternal side were detected with the aberrant chromosome. Replication studies were performed on cultures of maternal peripheral blood lymphocytes, and it was determined that the inverted X chromosome was early replicating in approximately half of the cells. Following genetic counseling, the pregnancy was continued and a healthy male infant was delivered at term. Cytogenetic analysis of peripheral blood performed in the newborn period confirmed the prenatal findings. The child is developing normally at 3 years of age.