Chromosomal inversion is a type of chromosomal aberration that occurs when a chromosome is rejoined by inverting a segment formed by two breaks by 180 degrees.
Paracentric inversions occur within the same arm and paracentric inversions occur between the long and short arms.
A pericentric inversion occurs between the long arm and the short arm.
The inter-arm inversion of chromosome 9 is a relatively common chromosomal variant, with an incidence of about 1.8% in the population. This chromosomal polymorphism is generally considered a normal variant, especially the pericentric inversion of chromosome 9 itself does not have pathological significance. Lv Liguo, Department of Urology, Guangdong Provincial Hospital of Traditional Chinese Medicine
However, chromosome 9 inversions are also associated with habitual abortion, stillbirth, and infertility, just like other chromosomal inversions. The inter-arm inversions form inversion loops during meiosis, and after separation of the four gametes, one is normal and one is inverted; the other two are unbalanced chromosomes, one of which may be lost and the other difficult to survive and cause miscarriage.
Therefore, it is not advisable to preserve the fetus in case of miscarriage with inter-arm inversion of chromosome 9. If the fetus dies after birth, genetic eugenics counseling should be done to find another cause of the infant’s death.
Studies have shown that the RLX gene is located on the pter-q12 segment of chromosome 9, and that RLX affects not only the maturation process of follicle development in females, but also the sperm motility and egg penetration ability in males. .
The adverse maternal history and infertility caused by inter-arm inversion of chromosome 9 should not be ignored clinically, and patients with inter-arm inversion of chromosome 9 should be investigated in their families to enhance prenatal diagnosis and guide their fertility in order to prevent the birth of children with chromosomal disorders.
Clinical and karyotype of 6 cases of inverted chromosome carriers
No.
Sex
Age
Clinical data
Karyotype
1
Male
31
Wife had 3 spontaneous abortions at 10-12w gestation
46XY,inv(7)(p11 p12)
2
female
34
The 1st and 3rd pregnancies were stillborn at 20-24w, and the 2nd pregnancy was spontaneously aborted at 10w.
2nd gestation 10w spontaneous abortion
46XX,inv(7)(q22 q35)
3
M
29
Wife had 3 spontaneous abortions at 8-12w gestation
46XY,inv(9)(p11 p12)
4
m
28
Wife had 2 spontaneous miscarriages at 8-12 weeks of gestation
46XY,inv(9)(p11 q13)
5
female
23
spontaneous miscarriage at 12w gestation
46XX,inv(9)(p11 q12)
6
m
27
wife had 3 spontaneous abortions,7-11w gestation
46XY,inv(13)(p11 q12)
(Quoted from “Analysis of the genetic effect of inversions between the arms of chromosome 9 in 75 cases”. Chinese Journal of Eugenics and Genetics, 2008, Vol. 16, No. 5, 42)