smartins

So after further analysis and comparison there has been a shift of diagnosis from insertion to inversion, which I'm told is more favorable in terms of prognosis. The inversion in the male fetus has been determined as essentially the same as the inversion in the mother: Mother karyotype = 46, X, inv(X)(p11.23q21.2) Male fetus karyotype = 46, Y, inv(X)(p11.23q21) Presently a chromosomal microarray is still pending on the mother and baby. Also a karyotype is being obtained on the mother's lone brother. We've been told that firstly because the pericentric inversion is apparently the same for the mother and baby that this is a good sign of normal phenotype. However the microarrays are needed for confirmation, particularly that there are no deletions or duplications of genetic information... balanced vs unbalanced inversion. We've also been told that if the mother's brother has the same pericentric inversion of the X chromosome this would be a favorable sign as well. One confusing issue seems to be that because a female has 2 X chromosomes, if one is inverted, abnormal or unbalanced, then it could be inactivated with preferential usage of the uninverted and normal X chromosome. So assuming that is the case (which isn't actually known in this instance), how is it truly favorable if the male fetus' pericentric inversion of the X chromosome is identical to the mother's if the male obviously won't have the luxury of an alternative X chromosome for usage? Beyond that, is it accurate to assume that if the pericentric inversion in the X chromosome in the male fetus is absent deletions or duplications (i.e. a balanced inversion), then the baby will be healthy/normal (i.e. absent consequences of the inversion other than possible reproductive issues)? Any thoughts or comments would be appreciated as well. Thank you.

Thank you for the reply. I understand how exceptionally rare this particularly chromosomal abnormality is. They are performing a SNP array analysis to detect unbalances (deletions or duplications) not detected by the amnio. My understanding is that if this is a "balanced" insertion then that is much more favorable to an unbalanced insertion. For instance, I read this on one website: "If someone carries a balanced insertional rearrangement, they should not have any symptoms (unless a critical gene is disrupted at the breakpoints) but they are at risk of producing a child with either a deletion or a duplication of chromosomal material but not both disorders." Would this appear to be accurate?

Hello, My family member is 20 weeks pregnant and has recently had an amniocentesis done to see if the fetus has any chromosomal abnormalities, as she herself has a pericentric inversion of the X chromosome. She is (46,X,inv (X) (p11.23q21.2)). She was told that she'd likely have a female child as inheritance in a male would be fatal and besides having difficulty becoming pregnant the likelihood of having issues in the offspring was low. However, after the amniocentesis, it has been discovered that it is indeed a male fetus that has an insertion instead of the expected inversion and is, 46,Y,ins(x)(p22.1q13q22). She is having difficulty gathering reliable and common information from the physicians she is dealing with and is desperate for more information. If anyone knows anything about these abnormalities, PLEASE help. We are running out of time