Fanconi anemia associated with increased nuchal translucency detected by first-trimester ultrasound

Fetal nuchal edema and developmental anomalies caused by gene mutations in mice

Fetal nuchal edema, a subcutaneous accumulation of extracellular fluid in the fetal neck, is detected as increased nuchal translucency (NT) by ultrasonography in the first trimester of pregnancy. It has been demonstrated that increased NT is associated with chromosomal anomalies and genetic syndromes accompanied with fetal malformations such as defective lymphatic vascular development, cardiac anomalies, anemia, and a wide range of other fetal anomalies. However, in many clinical cases of increased NT, causative genes, pathogenesis and prognosis have not been elucidated in humans. On the other hand, a large number of gene mutations have been reported to induce fetal nuchal edema in mouse models. Here, we review the relationship between the gene mutants causing fetal nuchal edema with defective lymphatic vascular development, cardiac anomalies, anemia and blood vascular endothelial barrier anomalies in mice. Moreover, we discuss how studies using gene mutant mouse models will be useful in developing diagnostic method and predicting prognosis.

An update on Fanconi anemia: Clinical, cytogenetic and molecular approaches (Review)

Fanconi anemia is a genetic syndrome clinically characterized by congenital malformations that affect several human systems, leads to progressive bone marrow failure and predisposes an individual to cancer, particularly in the urogenital area as well as the head and neck. It is commonly caused by the biallelic compromise of one of 22 genes involved in the FA/BRCA repair pathway in most cases. The diagnosis is based on clinical suspicion and confirmation using genetic analysis, where the chromosomal breakage test is considered the gold standard. Other diagnostic methods used include western blotting, multiplex ligation-dependent probe amplification and next-generation sequencing. This genetic condition has variable expressiveness, which makes early diagnosis difficult in certain cases. Although early diagnosis does not currently allow for improved cure rates for this condition, it does enable healthcare professionals to perform a specific systematic follow-up and, if indicated, a bone marrow transplantation that improves the mobility and mortality of affected individuals. The present review article is a theoretical revision of the pathophysiology, clinical manifestations and diagnosis methods intended for different specialists and general practitioners to improve the diagnosis of this condition.

Educating military primary health-care providers in genomic medicine: lessons learned from the MilSeq Project

PURPOSE

With few trained genetics professionals, the Military Health System is ill-equipped to manage the rapid expansion of genomic medicine. The MilSeq Project introduces an alternative service delivery model (ASDM) in which primary health-care providers (HCPs) provide post-test counseling (PTC) to healthy Airmen who have undergone exome sequencing. We describe HCP performance after a prerequisite educational intervention (EI).

METHODS

After a brief EI and pre-/posteducation surveys, HCPs were eligible to provide PTC with a genetic counselor available for consult. PTC was recorded, transcribed, and reviewed. Opportunities for improvement were organized into four error adjustment categories: (1) knowledge limitation, (2) minor, (3) moderate, and (4) critical. Thematic analysis was also performed.

RESULTS

Pre-/posteducation survey responses revealed statistically significant improvements in all domains. Minor error adjustments were most represented (n = 93), followed by knowledge limitation (n = 39) and moderate (n = 19). No critical errors were identified, and 17 transcripts required no adjustment. Thematic analysis revealed four themes that would benefit from more focused education: (1) family-centered care, (2) conveying risk, (3) disease knowledge, and (4) assay knowledge.

CONCLUSION

HCPs demonstrated competence in basic PTC after a brief EI. This ASDM may be a viable interim response to the shortage of genetics professionals in some systems.

Additional first-trimester ultrasound markers

The first trimester (11-13 +6 weeks) ultrasound examination is useful for several reasons: determination of an accurate date of confinement, diagnostic purposes, and screening for fetal defects. Nuchal translucency measurement combined with maternal serum markers (free b-human chorionic gonadotropin and pregnancy-associated plasma protein A) is the mainstay of first-trimester screening for chromosomal defects. However, over the past decade additional ultrasound markers have been developed that improve the performance of this type of screening. The novel markers include evaluation of the nasal bone, fronto-maxillary angle measurement, and Doppler evaluations of the blood flow across the tricuspid valve and in the ductus venosus.

First Trimester Ultrasound Screening: An Update

For many years, the main use of ultrasound in the first trimester of pregnancy was to confirm viability and to establish gestational age. Indeed, the crown-rump length measurement in the first trimester remains the most accurate method to estimate the gestational age even today. However, improvements in ultrasound equipment and improvement in our understanding of normal and abnormal fetal development allows us now to perform a much more complete first trimester fetal evaluation. This pertains not only to the diagnosis of fetal anomalies but also to screening for fetal defects. The combination of the nuchal translucency measurement and maternal serum biochemistries (free β-hCG and PAPP-A) has been shown to be an extremely efficient way to screen for fetal aneuploidy. The addition of other first trimester markers such as the nasal bone evaluation, frontomaxillary facial angle measurement, and Doppler evaluation of blood flow across the tricuspid valve and through the ductus venosus improves the screening performance even further by increasing the detection rates and decreasing the false positive rates. Several of the first trimester markers also are useful in screening for cardiac defects. Furthermore, significant nuchal translucency thickening has been associated with a variety of genetic and nongenetic syndromes. A recently described first trimester marker called the intracerebral translucency appears to hold great promise in screening for open spine defects. Finally, it appears that a first trimester evaluation (uterine artery Doppler and the measurement of certain biochemical markers in the maternal serum) significantly improves the assessment of the risk of preeclampsia.

First trimester ultrasonography in screening and detection of fetal anomalies

An obstetrical ultrasound examination provides invaluable information regarding the fetus. Until the mid-1980s, ultrasound in the first trimester was limited to localization of the pregnancy, establishing viability, and accurate dating. With the advent of high-resolution ultrasound and transvaginal scanning, a significant amount of information about the fetus can be gained and provided to the patient at a very early stage in gestation. This article provides an overview of the role of first trimester (11-13 + 6 weeks' gestation) ultrasound in screening and diagnosis of fetal anomalies. The first trimester is an ideal time for screening for aneuploidy, primarily due to the advantages that nuchal translucency (NT) measurement provides. NT measurement is also useful in establishing the risk of congenital cardiac disorders and a number of genetic and non-genetic syndromes. Significant NT thickening is associated with an increase in perinatal morbidity and mortality. Potential mechanisms resulting in increased NT are discussed. A number of new ultrasound markers for fetal aneuploidy have been investigated over the past several years, some of which appear to improve the screening efficacy of early ultrasonography. The role of these is reviewed. A number of fetal anomalies can now be consistently diagnosed in the first trimester. Their appearance at this early gestational age is discussed as well. It is clear that, data obtained by first trimester ultrasound are useful in counseling expectant parents and in planning the appropriate follow-up.

Prenatal exclusion/confirmation of Fanconi anemia via flow cytometry: a pilot study

OBJECTIVE

To explore the potential of flow cytometry in the prenatal exclusion or confirmation of Fanconi anemia (FA).

METHODS

Indications for prenatal diagnosis were (1) FA-negative family history, but suspicious ultrasound findings such as radial ray aplasia, (2) FA-positive family history, but without knowledge of the affected gene and/or mutation. Amniotic fluid (AF) cell cultures and umbilical cord (UC) blood cultures were assayed for typical cell cycle changes (G2-phase accumulations) without and with mitomycin C (MMC) treatments using single- and dual-parameter (BrdU-Hoechst) flow cytometry.

RESULTS

Single-parameter flow cytometry correctly identified 2 positive and 9 negative cases on the basis of MMC sensitivity of cultivated AF cells. Likewise, 8 negative and 2 positive cases were correctly predicted using bivariate flow cytometry of 72-hour UC blood cultures. In contrast, bivariate flow cytometry applied to AF cells grown in the presence of bromodeoxyuridine (BrdU) yielded false-positive and false-negative results.

CONCLUSIONS

Single-parameter flow cytometry of AF cell cultures and bivariate flow cytometry of UC cell cultures have the potential to correctly predict the affected status in cases at risk for FA, whereas bivariate flow cytometry proved unreliable when applied to BrdU-substituted AF cell cultures. Cases with a low a priori risk (e.g. sonographic finding of radial ray abnormalities and negative family history) would benefit most from flow cytometry as a rapid and economical prenatal screening procedure.

Increased nuchal translucency with normal karyotype

Increased fetal nuchal translucency (NT) thickness between 11 and 14 weeks' gestation is a common phenotypic expression of chromosomal abnormalities, including trisomy 21. However, even in the absence of aneuploidy, nuchal thickening is clinically relevant because it is associated with an increase in adverse perinatal outcome caused by a variety of fetal malformations, dysplasias, deformations, dysruptions, and genetic syndromes. Once the presence of aneuploidy is ruled out, the risk of perinatal outcome dose not statistically increase until the nuchal translucency measurement reaches 3.5 mm or more (>99th percentile). This increase in risk occurs in an exponential fashion as the NT measurement increases. However, if the fetus survives until midgestation, and if a targeted ultrasound at 20 to 22 weeks fails to reveal any abnormalities, the risk of an adverse perinatal outcome and postnatal developmental delay is not statistically increased.

Prenatal diagnosis of Fanconi anemia (Group C) subsequent to abnormal sonographic findings

Manifestations of Fanconi Anemia Complementation Group C (FA-C) include multiple major congenital malformations, hypoplastic radius, absent thumb, growth retardation, elfin-like facial features, microphthalmia, microcephaly, cafe-au-lait spots, early onset of hematologic disease and poor survival (Auerbach, 1997). We describe two cases in which second-trimester sonographic findings led to parental carrier testing for FA-C and subsequent prenatal diagnosis of affected fetuses.

Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities

There is extensive evidence that effective screening for major chromosomal abnormalities can be provided in the first trimester of pregnancy. Prospective studies in a total of 200,868 pregnancies, including 871 fetuses with trisomy 21, have demonstrated that increased nuchal translucency can identify 76.8% of fetuses with trisomy 21, which represents a false-positive rate of 4.2%. When fetal nuchal translucency was combined with maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A in prospective studies in a total of 44,613 pregnancies, including 215 fetuses with trisomy 21, the detection rate was 87.0% for a false-positive rate of 5.0%. Studies from specialist centers with 15,822 pregnancies, which included 397 fetuses with trisomy 21, have demonstrated that the absence of the nasal bone can identify 69.0% of trisomy 21 fetuses, which represents a false-positive rate of 1.4%. It has been estimated that first-trimester screening by a combination of sonography and maternal serum testing can identify 97% of trisomy 21 fetuses, which represents a false-positive rate of 5%, or that the detection rate can be 91%, which represents a false-positive rate of 0.5%. In addition to increased nuchal translucency, important sonographic markers for chromosomal abnormalities, include fetal growth restriction, tachycardia, abnormal flow in the ductus venosus, megacystis, exomphalos and single umbilical artery. Most pregnant women prefer screening in the first, rather than in the second, trimester. As with all aspects of good clinical practice, those care givers who perform first-trimester screening should be trained appropriately, and their results should be subjected to external quality assurance.

Comparison of pregnancy outcome of euploid fetuses with increased nuchal translucency (NT) expressed in NT MoM or delta-NT

OBJECTIVE

To evaluate the outcome of euploid fetuses with increased nuchal translucency thickness (NT) expressed in multiples of the median (MoM) or delta-NT.

METHODS

Included in the study were euploid fetuses with increased NT >or= 95(th) centile, for which information about pregnancy outcome was available. The following parameters were defined as an adverse outcome: miscarriage, structural anomalies justifying termination of pregnancy, and structural anomalies, genetic syndromes and neurodevelopmental problems diagnosed postnatally. Fetal outcome according to NT MoM and delta-NT was calculated using different cut-off values. Calculations of the odds ratio for adverse outcome were performed using either NT MoM or delta-NT as a predictor in logistic regression models.

RESULTS

The study comprised 168 euploid fetuses. Of these, 38 (23%) had an adverse outcome: 11 (6%) had miscarriages, 14 (8%) were terminated because of fetal abnormalities detected on the prenatal scan and 13 (7%) were found postnatally to have abnormalities. The incidence of cases exhibiting an adverse outcome was 5.3%, 19.2% and 58.5% for NT values of 1.6-1.9, 2.0-3.0 and >3.0 MoM, respectively (P < 0.0001, chi(2) test), and 3.9%, 16.7% and 62.8% for delta-NT values of 1.0-1.4, 1.5-2.5 and >2.5 mm, respectively (P < 0.0001, chi(2) test). Using cut-offs of 2.0 MoM and delta-NT of 1.5 mm, the odds ratios for adverse outcome were 10.2 (95% CI, 3.4-30.4) and 15.4 (95% CI, 4.2-43.6), respectively.

CONCLUSION

Both the NT MoM and delta-NT approaches may be used to determine cases which require additional antenatal investigation as well as fetal karyotyping. For this purpose we suggest using a cut-off of either 2.0 MoM or a delta-NT of 1.5 mm.

Cancer in Fanconi anemia, 1927-2001

BACKGROUND

Fanconi anemia (FA) is an autosomal recessive disease associated with an abnormal response to DNA damage. Although FA is well known for the association of aplastic anemia and characteristic birth defects, leukemia and solid tumors also occur at a high rate in this group of patients. A review of all reported cases is informative with regard to the specific types of cancer, the ages at which they occur, and the cumulative probability of their development.

METHODS

Medline and bibliographies of publications were searched for articles containing "Fanconi's anemia" or "aplastic anemia" and all cases of FA from 1927 through 2001 were included in the database. Cancer cases were identified within these reports. Descriptive statistical analyses were performed using Stata7 software.

RESULTS

One thousand three hundred cases of FA were identified. Nine percent had leukemia (primarily acute myeloid leukemia), 7% had myelodysplastic syndrome, 5% had solid tumors, and 3% had liver tumors. Patients with cancer were older than the cancer-free patients at the time of diagnosis of FA. The median age for cancer (including leukemia) was 16, compared with 68 in the general population. The most frequent solid tumors were aerodigestive and gynecological carcinomas. In approximately 25% of patients with cancer, the malignancy preceded the diagnosis of FA.

CONCLUSIONS

If the competing risks of aplastic anemia and leukemia could be removed, the estimated cumulative probability of development of a solid tumor in FA patients is 76% by the age of 45 years. Carcinogenic pathways and cancer prevention, surveillance, and treatment can be studied to advantage in this genetic model of human cancer.

The role of fetal nuchal translucency in prenatal screening

PURPOSE OF REVIEW

An update of findings from studies on first trimester nuchal translucency screening.

RECENT FINDINGS

New first trimester markers can substantially improve efficacy of screening. When fully informed, preliminary data indicate that women prefer first trimester above second trimester testing.

SUMMARY

Recent reports on nuchal translucency screening reiterate the importance of standardization of technique and quality control as proposed by the Fetal Medicine Foundation in London. Effective quality control can be achieved through quantitative analysis of operator specific data. Three-dimensional ultrasound does not provide substantially higher success rates in obtaining reliable nuchal translucency measurements than two-dimensional ultrasound. New data confirm the previously reported association between increased nuchal translucency and increased rate of spontaneous fetal loss, genetic syndromes and a high prevalence (15%) of anomalies, among which cardiac defects are the commonest. Researchers agree that increased nuchal translucency ought to be an indication for specialized echocardiography. Promising data have become available on new markers that can enhance first trimester screening. It is estimated that when assessment of nasal bone and maternal serum analytes are taken into account, first trimester screening can identify 97.5% of trisomy 21 pregnancies for a 5% false-positive rate. It is stressed that parents need to be informed about the possible implications of screening before testing. Preliminary data indicate that when appropriately informed, women prefer first trimester above second trimester testing. Furthermore, the uptake of screening is likely to be relatively low among younger women.

Outcome of pregnancy in chromosomally normal fetuses with increased nuchal translucency in the first trimester

OBJECTIVES

To study the outcome of chromosomally normal pregnancies with increased nuchal translucency at the 10-14-week scan.

DESIGN

Retrospective study of 1320 chromosomally normal singleton pregnancies with nuchal translucency of > or = 3.5 mm. In addition to fetal karyotyping these patients were managed with follow-up scans at 14-16 and 20-22 weeks, specialist fetal echocardiography and in selected cases by infection screening and further genetic testing.

RESULTS

In the 1320 pregnancies there were 68 (5.15%) spontaneous abortions or intrauterine deaths, 18 (1.36%) neonatal and infant deaths and 154 (11.67%) terminations of pregnancy. In the 1080 (81.82%) survivors, 60 (5.56%) had abnormalities requiring medical or surgical treatment or leading to mental handicap. The chance of a livebirth with no defects in the group with nuchal translucency of 3.5-4.4 mm was 86%, for those with translucency of 4.5-5.4 mm it was 77%, for those with translucency of 5.5-6.4 mm it was 67%, and for those with translucency of > or = 6.5 mm it was 31%.

CONCLUSIONS

Increased fetal nuchal translucency is associated with chromosomal abnormalities, many fetal defects and genetic syndromes. In the majority of cases a series of antenatal investigations, including fetal karyotyping, detailed scans, fetal echocardiography, as well as genetic testing and infection screening, that can be completed by 20 weeks of gestation would distinguish between the pregnancies destined to result in adverse outcome and those leading to the delivery of infants without major defects.