45,X/46,XY mosaicism: the role of ultrasound in prenatal diagnosis and counselling

High-level mosaicism for 45,X in 45,X/46,X,idic(Y)(q11.2) at amniocentesis in a pregnancy with a favorable outcome and postnatal progressive decrease of the 45,X cell line

OBJECTIVE

We present prenatal diagnosis of high-level mosaicism for 45,X in 45,X/46,X,idic(Y)(q11.2) at amniocentesis in a pregnancy with a favorable outcome and postnatal progressive decrease of the 45,X cell line.

CASE REPORT

A 36-year-old, gravida 4, para 3, woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 45,X[22]/46,X,idic(Y)(q11.2)[4]. Prenatal ultrasound was unremarkable, and the fetus had normal male external genitalia. Repeat amniocentesis was performed at 20 weeks of gestation, and the second amniocentesis revealed a karyotype of 45,X[24]/46,X,idic(Y)(q11.2)[3]. Simultaneous interphase fluorescence in situ hybridization (FISH) analysis on uncultured amniocytes revealed that 60% (62/103 cells) were Y-deleted cells. After genetic counseling, the parents decided to continue the pregnancy, and a 3020-g male baby was delivered with a body length of 52 cm, normal male genital organs and no phenotypic abnormalities. The karyotypes of cord blood, umbilical cord and placenta were 45,X[20]/46,X,idic(Y)(q11.2)[20], 45,X[31]/46,X,idic(Y)(q11.2)[9] and 45,X[40], respectively. At age one month, FISH analysis on urinary cells and buccal mucosal cells revealed 11.5% (7/61 cells) and 13.6% (16/118 cells), respectively for mosaicism for the Y-deleted cells. At age five month, the karyotype of peripheral blood was 45,X[9]/46,X,idic(Y)(q11.2)[31]. FISH analysis on buccal mucosal cells showed no abnormal Y-deleted cell (0/101 cells). At age 11 month, the karyotype of peripheral blood was 45,X[5]/46,X,idic(Y)(q11.2)[35]. FISH analysis on 102 buccal mucosal cells showed no abnormal signals. The infant was doing well with normal physical and psychomotor development.

CONCLUSION

High-level mosaicism for 45,X in 45,X/46,X,idic(Y)(q11.2) at amniocentesis can be associated with a favorable outcome and progressive decrease of the 45,X cell line.

Perinatal cytogenetic discrepancy in a pregnancy with mosaic 45,X/46, XY at amniocentesis and a favorable outcome

OBJECTIVE

We present perinatal cytogenetic discrepancy in a pregnancy with mosaic 45,X/46, XY at amniocentesis and a favorable outcome.

CASE REPORT

A 38-year-old, primigravid woman underwent amniocentesis at 17 weeks of gestation because of advanced maternal age. Amniocentesis revealed a karyotype of 45,X[2]/46,XY[6]. Level II ultrasound at 20 weeks of gestation was unremarkable, and the fetus had normal male external genitalia. Following genetic counseling, the woman decided to continue the pregnancy. At 39 weeks of gestation, a healthy male baby was delivered with a body weight of 3410 g and a body length of 54.5 cm. The male external genital organs were normal. The cord blood had a karyotype of 46, XY (40/40 cells). The umbilical cord had a karyotype of 45,X[1]/46,XY[39]. During follow-up at age one month, his body weight was 4.4 Kg (15th-50th centile), and his body length was 56 cm (50th-85th centile). The infant was doing well. Interphase fluorescence in situ hybridization analysis on 100 buccal mucosal cells revealed no abnormal Y-deletion cell, and all cells contained one Y signal.

CONCLUSION

Perinatal cytogenetic discrepancy may occur in the pregnancy with mosaic 45,X/46, XY at amniocentesis.

Accuracy of perinatal diagnosis of 45,X/46,XY mosaicism and electronic consultation of affected parents

OBJECTIVE

To assess parental satisfaction with e-mail consultations and fetal outcomes after consultation for offspring with 45,X/46,XY mosaicism.

PATIENTS AND METHODS

A chart review was performed of prenatal and postnatal e-mail consultations concerning 45,X/46,XY mosaicism at our institution. Prenatally, mosaicism was detected by amniocentesis; postnatally by phenotype and subsequent genotyping. Parents e-mailed us for a second opinion after internet searches. Follow-up parental satisfaction was evaluated by e-mail.

RESULTS

E-mail consultation occurred in six prenatal and eight postnatal cases. One of the eight postnatal cases had a prenatal diagnosis but without our second opinion. In 7/8 postnatal cases, abnormal neonatal phenotype was evaluated by genotyping. Termination of pregnancy was a consideration in all six prenatal consultations, although not discussed by us. One fetus was stillborn. Postnatal karyotype was mosaic in 11/13 surviving neonates. Phenotypes in surviving fetuses were normal male (2/13), hypospadias and an undescended testis or streak gonad (9/13), female with mild clitoral hypertrophy (1/13), and normal female (1/13). The stillborn fetus was noted only to have a penis.

CONCLUSION

All parents reported in follow up that e-mail consultations provided them with enhanced clinical information, allowing them to make better informed clinical decisions.

Fetal gender: antenatal discrepancy between phenotype and genotype

Sexual discrepancy is reported in both 46,XY females and 46,XX males, and most diagnoses of sex reversal are made in the postpubertal period. We report three cases of sexual discrepancy, which were revealed by karyotyping following genetic amniocentesis, chorionic villus sampling and fetal blood sampling. The etiologies of 46,XX male, 45,X male and 46,XY female subjects are reviewed. When sexual discrepancy between fetal karyotype and ultrasonographic fetal phenotype is encountered, sample error and placental mosaicism should be excluded. A detailed fetal ultrasound examination should be performed to check for syndromic gender discrepancy. When repeat karyotyping is indicated, localization of the Sox related Y chromosome gene should be carried out.

Sex chromosome mosaicism in males carrying Y chromosome long arm deletions

Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility. Since large structural rearrangements of the Y chromosome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we studied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertile men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR). Patients were divided into two groups: group 1 (n = 6), in which karyotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) with apparently a normal 46,XY karyotype. 45,XO cells were identified by fluorescence in-situ hybridization (FISH) using X and Y centromeric probes. Lymphocytes from 11 fertile men were studied as controls. In addition, sperm cells were studied in three oligozoospermic patients in group 2. Our results showed that large and submicroscopic Yq deletions were associated with significantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic methods, were detected. Therefore, Yq microdeletions may be associated with Y chromosomal instability leading to the formation of 45,XO cell lines.

Fetal sex determination by high resolution ultrasound in early pregnancy

OBJECTIVE

Fetal sex determination by ultrasound, and its medical and ethical implications, has been predominantly discussed in mid and late gestation. The development of high resolution ultrasound equipment has provided the possibility of detailed visualization of the fetus in early pregnancy. The present prospective study investigates the feasibility and accuracy of fetal sex determination by transabdominal ultrasound in early pregnancy.

METHODS

Sonographic determination of fetal sex was attempted prospectively prior to genetic amniocentesis in 173 fetuses from 11 to 16 weeks of gestation. The result of ultrasound examination was compared with the karyotype obtained from amniotic fluid cells.

RESULTS

Sonographic sex determination was feasible in 80.3% of cases, and all these determinations proved to be correct. There was no difference in the identification rate between male (n=87) and female (n=86) sex. Fetal sex determination was also feasible and correct in all four sets of twins and in the one set of quadruplets.

CONCLUSION

Fetal sex assignment in the late first and early second trimester can be useful in pregnancies at risk for severe sex-linked diseases, in fetal disorders involving the genitalia, and in the individual identification of multiple fetuses. Prenatal sex assignment in early pregnancy implicates also far-reaching ethical problems because of the potential risk of sex-selected abortion.