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PubMed2006

Mosaic trisomy 16 in a fetus: the complex relationship between phenotype and genetic mechanisms.

OBJECTIVES: This study was undertaken to discuss the workup of trisomy 16 pregnancies. STUDY DESIGN: This case study reports the prenatal detection and postnatal confirmation of mosaic trisomy 16, associated with uniparental disomy (UPD) 16, in a 34-year-old woman who showed elevated maternal serum alpha-fetoprotein and beta-HCG at a gestational age (GA) of 15.5 weeks. RESULTS: Amniotic fluid (AF) karyotyping at different GAs revealed various levels of trisomy 16 mosaicism (0 to level III). UPD studies at 21 weeks of gestation revealed maternal heterodisomy 16. Serial fetal ultrasonography showed fetal abnormalities: intrauterine growth restriction (IUGR), dilated digestive tract, and gallbladder agenesis. Postmortem examination confirmed the prenatal findings and revealed additional anomalies, such as hypoplastic cerebellum with abnormal gyration of the vermis. CONCLUSIONS: Workup following prenatal detection of trisomy 16 mosaicism in chorionic villi must include AF karyotyping and serial ultrasound examination of the fetus in order to approach postnatal developmental prognosis.

Abortion, Induced↗
PubMed1982

Trisomy 20 mosaicism in amniotic fluid cells.

The significance of trisomy 20 mosaicism in cultured amniotic fluid cells is still confusing. We report a case of amniotic cell normal/trisomy 20 mosaicism diagnosed prenatally. The pregnancy was carried to term and a normal baby girl was delivered. The authors consider that in cases of amniotic fluid cell normal/trisomy 20 mosaicism the termination of pregnancy may not be advised, however, the parents should be fully informed.

Adult↗
PubMedDate not supplied

Fetoscopy and fetal blood sampling in the management of a twin pregnancy with 45,X/46,XX amniotic fluid cell mosaicism and a suspected fluid sampling error.

A 37 year-old woman with a twin pregnancy underwent amniocentesis to exclude fetal chromosome abnormality. The results indicated that both fetuses were mosaics, with 45,X and 46,XX, cell lines. Since it was suspected from the ultrasound scan that the twins were dizygotic, the result was questioned. Fetoscopy and fetal blood sampling were performed and karyotyping the fetal lymphocytes confirmed that one twin was indeed a mosaic, 45,X/46,XX, but the other had a normal male chromosome complement. The pregnancy resulted in the birth of a phenotypically normal girl, in whom the 45,X/46,XX mosaicism was confirmed, and a normal boy.

Adult↗
PubMedDate not supplied

Further examples of trisomy-20 mosaicism in amniotic cell cultures.

Amniotic fluid cultures from two patients showed trisomy-20 mosaicism. No trisomy-20 cells were found in a normal full term infant and in multiple tissue biopsies and fetal blood from a fetus after a termination of pregnancy. No definitive advice is yet possible for parents where trisomy-20 amniotic cell mosaicism is detected. Fetoscopy and fetal blood sampling are of no value and termination of pregnancy is not indicated by empirical evidence. Preferential trophoblastic non-disjunction (Kalousek and Dill, 1983) is discussed as a possible partial explanation for the variable occurrence and distribution of this type of mosaicism.

Adult↗
PubMed1987

Prenatal diagnosis of mosaic trisomy 9.

Mosaic trisomy 9 was detected in an amniotic fluid cell culture from a 40-year-old woman evaluated because of advanced maternal age. After counselling, parents elected to terminate the pregnancy. On autopsy the fetus was found to have hydrocephalus and a single kidney. The diagnosis of trisomy 9 mosaicism was confirmed in cultured skin fibroblasts. This is the third reported case of trisomy 9 mosaicism diagnosed prenatally.

Adult↗
PubMed1987

Prenatal diagnosis of trisomy 20 mosaicism indicating an extra embryonic origin.

An additional case of amniotic fluid trisomy 20 mosaicism is presented. After careful counselling, the pregnancy continued and a phenotypically normal female was delivered. This case of amniocyte mosaicism establishes the source of aneuploid cell line as amnion. Since an extra-embryonic origin of the mosaicism has been confirmed, this should be carefully considered as a real possibility in counselling such families.

Chromosomes, Human, Pair 20↗
PubMed1987

Trisomy 20 mosaicism in prenatal diagnosis--a review and update.

A total of 66 cases with prenatal diagnosis of trisomy 20 mosaicism was reviewed. Since the majority of cases (85 per cent) was associated with grossly normal phenotype and the abnormalities noted in 15 per cent of cases were inconsistent and rather non-specific, no casual relationship between trisomy 20 mosaicism and a specific malformation syndrome can be established. The possibility of an association between an abnormal phenotype and a high percentage of trisomy 20 cells (greater than 60 per cent) must be considered preliminary and be viewed with caution. The fact that cells with trisomy 20 have not been recovered from blood cultures and were detected more frequently from specific fetal tissues, (such as kidney, rectum, oesophagus), and from placental tissues, suggests that trisomy 20 is more likely to be confined to certain fetal organs and to extra-embryonic tissues. This review calls for the collection of more data on all cases of trisomy 20 mosaicism diagnosed prenatally, in order to provide more accurate information to the prospective parents.

Chromosome Aberrations↗
PubMed1988

Maternal sex chromosome mosaicism diagnosed by amniocentesis and percutaneous umbilical cord sampling.

We present a remarkable chain of events in which percutaneous umbilical cord sampling was performed in an attempt to clarify a situation of possible fetal sex chromosome mosaicism in an amniotic fluid culture and led to the discovery that the mother herself had a 45,X/46,XX/47,XXX chromosome constitution. This may have simply represented the chance concurrence of pseudo-mosaicism in the amniotic fluid culture of a woman with an abnormal sex chromosome constitution, but it is also possible that the 45,X colony was maternal in origin. Although clearly a most unusual circumstance, the possibility should be kept in mind when termination of a pregnancy is being considered because of apparent mosaicism in a prenatal diagnostic study.

Adult↗
PubMed1989

Prenatal diagnosis of 45,X/46,XY mosaicism--a review and update.

A total of 54 cases with prenatal diagnosis of 45,X/46,XY mosaicism was reviewed. Of 47 cases with information on phenotypic outcome, 42 cases (89.4 per cent) were reported to be associated with a grossly normal male phenotype. Three cases (6.4 per cent) were diagnosed as having mixed gonadal dysgenesis with internal asymmetrical gonads. Two other cases were questionably abnormal. In 40 cases with successful cytogenetic confirmatory studies, the overall rate of cytogenetic confirmation of 45,X/46,XY from tissues derived from fetus/liveborn/placenta was 70.0 per cent. This review shows a major difference in the phenotypic outcome between postnatal diagnosis and prenatal diagnosis. Due to the ascertainment bias, almost all known patients with postnatal diagnosis of 45,X/46,XY mosaicism are phenotypically abnormal. Therefore, caution must be used in translating information derived from postnatal diagnosis to prenatal diagnosis. This review calls for collection of more data on 45,X/46,XY mosaicism diagnosed prenatally, more long-term follow-up of liveborn infants, and pathological studies of all abortuses. Emphasis is placed also on the importance of genetic counselling, ultrasound examination, and cytogenetic confirmation.

Amniotic Fluid↗
PubMed1989

Trisomy 20 mosaicism confirmed in a phenotypically normal liveborn.

Prenatal diagnosis of trisomy 20 mosaicism in this case was based on cytogenetic analysis of cultured amniotic fluid cells (23/252 cells were trisomy 20 representing cells from each of four primary cultures). The pregnancy continued to term and the mosaicism was confirmed in the phenotypically normal male neonate by analysis of cultured foreskin fibroblasts (7/49 cells + 20) and placental cells 20/20 cells + 20) whereas the peripheral lymphocytes were cytogenetically normal (20/20 cells were 46,XY). This represents the first confirmation of trisomy 20 mosaicism in a phenotypically normal full-term neonate.

Adult↗
PubMed1990

Trisomy 12 mosaicism in phenotypically normal fetuses following prenatal detection.

We report three cases of amniocentesis in which mosaicism for trisomy 12 was detected in two or more independent cultures. The parents elected to terminate the pregnancy in all three cases. Follow-up studies in two of the cases confirmed the mosaicism in fetal tissues (in subcutaneous tissue in one case; in fetal lung in the other), but not in blood. No fetal anomalies were evident by ultrasound or at autopsy. These results along with other reported cases demonstrate the difficulty in counselling for mosaic trisomy 12.

Adult↗
PubMed1990

Discordant findings in chorionic villus direct preparation and long term culture--mosaicism in the fetus.

Prenatal cytogenetic study of chorionic villi showed a discrepancy between a normal female karyotype 46,XX in the direct preparation after short-term incubation, and a 45,X karyotype in the long-term culture. The subsequent amniocentesis revealed a normal karyotype in three cultures and a 45,X/46,XX mosaicism in one culture. Cytogenetic analysis of chorionic villi after termination of the pregnancy showed a normal karyotype in the direct preparation and a 45,X/46,XX mosaicism in the long-term culture. Fetal lymphocytes showed normal karyotypes, whereas fibroblast cultures revealed a 45,X/46,XX mosaicism.

Chorionic Villi Sampling↗
PubMed1990

Trisomy 12 mosaicism detected by mid-trimester amniocentesis.

Trisomy 12 mosaicism was found in about 15 per cent of cultured amniocytes obtained from a 32-year-old white female at 17.6 weeks of gestation. Termination of pregnancy was elected and multiple tissues were obtained for chromosome analysis. Of 158 cells examined, only 1 cell in placenta was found with an extra number 12 chromosome. Pathological examination of the fetus did not reveal significant physical abnormalities. This report illustrates the difficulty of confirming trisomy 12 mosaicism which has been detected on prenatal diagnosis. The presence of trisomy 12 in one placental cell obtained from the curettage specimen suggests the possibility of confined placental mosaicism in this case.

Adult↗
PubMed1991

'False-negative' and 'false-positive' prenatal cytogenetic results due to 'true' mosaicism.

A 37-year-old gravida was referred for CVS because of advanced maternal age. A trisomy 21 was present in all cells after short-term incubation (direct processing (DP)) and long-term culture. According to our policy, a retap was offered for confirmation of the result during the legally required 3-day waiting period between communication of the result and termination of pregnancy. Unexpectedly all cells after DP showed a normal male chromosome complement. Further investigations revealed mosaicism in trophoblast tissue and a normal karyotype in amniotic fluid cells and fetal blood (50 mitoses each). The parents elected to continue the pregnancy after extensive ultrasound examinations did not show suspicious findings. After the birth of a healthy child, cell cultures from ten different placental sites confirmed mosaicism. Four out of 100 mitoses from a lymphocyte culture showed an additional chromosome 21. The child had no dysmorphic features and the development was normal at the age of 10 weeks. This case demonstrates the restricted validity of prenatal cytogenetic analysis in the presence of true fetal mosaicism. It also stresses the benefit of our policy to offer a retap in cases with abnormal cytogenetic results prior to termination of pregnancy which is considered unnecessary by many cytogeneticists.

Adult↗
PubMed1991

Prenatal diagnosis and outcomes of five cases of mosaicism for an isochromosome of 20q.

Five cases of mosaicism for an isochromosome of 20q have been detected from a total of 50,000 cases analysed for prenatal diagnosis by amniocentesis. Karyotypes were designated mos 46,X-/46,X-,i(20q). In all cases, the abnormal cell line was detected in more than one primary culture, thus fulfilling the criterion for true (level III) mosaicism. Indications for prenatal diagnosis were parental anxiety (two cases), low maternal serum alpha-fetoprotein (AFP) (two cases), and high maternal serum AFP (one case). Level II ultrasounds on all five fetuses were normal, and the abnormal cell line was never detected in fetal blood and/or cord blood. All five pregnancies were continued and had normal outcomes, with birth weights ranging from 2.4 to 3.8 kg. The development of all five children has been normal, with the oldest child in the study now 4 years of age. We suggest that the abnormal cell line in each case was of extrafetal origin, and that this may be one of the more common examples of this phenomenon, occurring in approximately 1/10,000 prenatal diagnoses. Mosaicism i(20q) may have been missed in the past because of the higher resolution necessary to detect this subtle change.

Adult↗
PubMed1991

Uncommon chromosomal mosaicism in chorionic villi.

Three cases of unusual chromosomal mosaicism are reported for which the cytogenetic data show inconsistent findings between CVS and AC or fetal tissue, and which cannot be explained simply by non-disjunction. For case 1, in CVS the karyotype was 46,XY, whereas lymphocytes and fibroblasts revealed 69,XXY. DNA fingerprinting indicated one paternal and two maternal chromosome sets, the latter most probably due to omission of maternal meiosis II. For case 2, in CVS mos 46,XX/47,XX,+ mar de novo was observed. Amniotic fluid cells had the karyotype 46,XX. The origin of the marker chromosome might be explained by at least two events of unknown order (a somatic chromosome/chromatid deletion and non-disjunction of the homologous chromosome). In case 3 (CVS: mos 46,XY/46,XY,19q+ de novo; amniotic fluid cells, lymphocytes, and fibroblasts: 46,XY), the surplus of chromosome material in 19q+ might be explained on the basis of a somatic translocation. The idea of a chimera is less convincing, as the mosaic finding is restricted to one tissue. Furthermore, there was no hint of a vanishing twin. Hitherto, no case of structural chromosome mosaicism in CVS has been reconfirmed in fetal tissues.

Adult↗
PubMed1991

Follow-up and pregnancy outcome after a diagnosis of mosaicism in CVS.

In 2103 consecutive diagnostic chorionic villus samples, examined in a 4-year period in our clinical genetics unit, 26 samples (1.2 per cent) presented chromosomal mosaicism in the direct and/or long-term culture preparations. Only once (46,XX/47,XX,+9) was the mosaicism confirmed in the fetus. In the cytogenetic follow-up studies of the remaining 25 pregnancies, in no cases could the aberration be confirmed in amniotic fluid or fetal tissue. One patient requested a termination after the CVS result. Of the remaining 24 pregnancies, four (16.7 per cent) ended in a spontaneous abortion. These findings suggest an association between placental mosaicism and fetal loss.

Abortion, Spontaneous↗
PubMed1992

Placental mosaicism in a case of 46,XY,-22,+t(22;22)(p11;q11) or i(22q) diagnosed at amniocentesis.

46,XY,-22,+t(22;22)(p11;q11) or i(22q) was diagnosed in 15/15 cells from two cultures from the amniotic fluid culture of a 31-year-old patient whose fetus demonstrated cystic hygroma on ultrasound. Cytogenetic studies performed on fetal skin from the abortus revealed the same karyotype as that seen on amniocentesis, but the placenta demonstrated a 46,XY/46,XY,-22,+t(22;22) or i(22q) mosaicism, with 65 per cent of the cells being 46,XY. This case provides an example of placental mosaicism for a normal male karyotype, while the fetus demonstrated non-mosaic trisomy 22.

Adult↗