Genotype-Phenotype Correlation in NF1: Evidence for a More Severe Phenotype Associated with Missense Mutations Affecting NF1 Codons 844-848.

Neurofibromatosis type 1 (NF1), a common genetic disorder with a birth incidence of 1:2,000-3,000, is characterized by a highly variable clinical presentation. To date, only two clinically relevant intragenic genotype-phenotype correlations have been reported for NF1 missense mutations affecting p.Arg1809 and a single amino acid deletion p.Met922del. Both variants predispose to a distinct mild NF1 phenotype with neither externally visible cutaneous/plexiform neurofibromas nor other tumors. Here, we report 162 individuals (129 unrelated probands and 33 affected relatives) heterozygous for a constitutional missense mutation affecting one of five neighboring NF1 codons-Leu844, Cys845, Ala846, Leu847, and Gly848-located in the cysteine-serine-rich domain (CSRD). Collectively, these recurrent missense mutations affect ∼0.8% of unrelated NF1 mutation-positive probands in the University of Alabama at Birmingham (UAB) cohort. Major superficial plexiform neurofibromas and symptomatic spinal neurofibromas were more prevalent in these individuals compared with classic NF1-affected cohorts (both p < 0.0001). Nearly half of the individuals had symptomatic or asymptomatic optic pathway gliomas and/or skeletal abnormalities. Additionally, variants in this region seem to confer a high predisposition to develop malignancies compared with the general NF1-affected population (p = 0.0061). Our results demonstrate that these NF1 missense mutations, although located outside the GAP-related domain, may be an important risk factor for a severe presentation. A genotype-phenotype correlation at the NF1 region 844-848 exists and will be valuable in the management and genetic counseling of a significant number of individuals.

Correction: Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

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Expanding the clinical phenotype of individuals with a 3-bp in-frame deletion of the NF1 gene (c.2970_2972del): an update of genotype-phenotype correlation.

PURPOSE: Neurofibromatosis type 1 (NF1) is characterized by a highly variable clinical presentation, but almost all NF1-affected adults present with cutaneous and/or subcutaneous neurofibromas. Exceptions are individuals heterozygous for the NF1 in-frame deletion, c.2970_2972del (p.Met992del), associated with a mild phenotype without any externally visible tumors. METHODS: A total of 135 individuals from 103 unrelated families, all carrying the constitutional NF1 p.Met992del pathogenic variant and clinically assessed using the same standardized phenotypic checklist form, were included in this study. RESULTS: None of the individuals had externally visible plexiform or histopathologically confirmed cutaneous or subcutaneous neurofibromas. We did not identify any complications, such as symptomatic optic pathway gliomas (OPGs) or symptomatic spinal neurofibromas; however, 4.8% of individuals had nonoptic brain tumors, mostly low-grade and asymptomatic, and 38.8% had cognitive impairment/learning disabilities. In an individual with the NF1 constitutional c.2970_2972del and three astrocytomas, we provided proof that all were NF1-associated tumors given loss of heterozygosity at three intragenic NF1 microsatellite markers and c.2970_2972del. CONCLUSION: We demonstrate that individuals with the NF1 p.Met992del pathogenic variant have a mild NF1 phenotype lacking clinically suspected plexiform, cutaneous, or subcutaneous neurofibromas. However, learning difficulties are clearly part of the phenotypic presentation in these individuals and will require specialized care.

Maternal plasma DNA testing for aneuploidy in pregnancies achieved by assisted reproductive technologies.

PURPOSE: We sought to compare measurements of circulating cell-free DNA as well as Down syndrome test results in women with naturally conceived pregnancies with those conceived using assisted reproductive technologies. METHODS: Data regarding assisted reproductive technologies were readily available from seven enrollment sites participating in an external clinical validation trial of nested case/control design. Measurements of circulating cell-free fetal and total DNA, fetal fraction (ratio of fetal to total DNA), chromosome-specific z-scores, and karyotype results were available for analysis. RESULTS: Analyses were restricted to 632 euploid (5.2% assisted reproductive technologies) and 73 Down syndrome (13.7% assisted reproductive technologies), including 16 twin pregnancies. No differences were found for fetal or total circulating cell-free DNA, or for the fetal fraction in euploid (P = 0.70) or Down syndrome (P = 0.58) pregnancies by method of conception. There appeared to be systematic z-score reductions for chromosomes 21, 18, and 13 in assisted reproductive technologies versus natural euploid pregnancies (P = 0.048, 0.0032, and 0.36, respectively). CONCLUSION: Assisted reproductive technologies and naturally conceived pregnancies contribute similar levels of circulating cell-free DNA into maternal circulation. Small differences in the z-scores of pregnancies achieved by assisted reproductive technologies were observed and do not appear to be test-related artifacts. However, the findings need confirmation before any consideration of changes to testing and reporting protocols.

Genomic characterization of prenatally detected chromosomal structural abnormalities using oligonucleotide array comparative genomic hybridization.

Detection of chromosomal structural abnormalities using conventional cytogenetic methods poses a challenge for prenatal genetic counseling due to unpredictable clinical outcomes and risk of recurrence. Of the 1,726 prenatal cases in a 3-year period, we performed oligonucleotide array comparative genomic hybridization (aCGH) analysis on 11 cases detected with various structural chromosomal abnormalities. In nine cases, genomic aberrations and gene contents involving a 3p distal deletion, a marker chromosome from chromosome 4, a derivative chromosome 5 from a 5p/7q translocation, a de novo distal 6q deletion, a recombinant chromosome 8 comprised of an 8p duplication and an 8q deletion, an extra derivative chromosome 9 from an 8p/9q translocation, mosaicism for chromosome 12q with added material of initially unknown origin, an unbalanced 13q/15q rearrangement, and a distal 18q duplication and deletion were delineated. An absence of pathogenic copy number changes was noted in one case with a de novo 11q/14q translocation and in another with a familial insertion of 21q into a 19q. Genomic characterization of the structural abnormalities aided in the prediction of clinical outcomes. These results demonstrated the value of aCGH analysis in prenatal cases with subtle or complex chromosomal rearrangements. Furthermore, a retrospective analysis of clinical indications of our prenatal cases showed that approximately 20% of them had abnormal ultrasound findings and should be considered as high risk pregnancies for a combined chromosome and aCGH analysis.

Clinical and genomic characterization of distal duplications and deletions of chromosome 4q: study of two cases and review of the literature.

Variable clinical presentations of patients with chromosomally detected deletions in the distal long arm (q) of chromosome 4 have been reported. The lack of molecular characterization of the deletion sizes and deleted genes hinders further genotype-phenotype correlation. Using a validated oligonucleotide array comparative genomic hybridization (oaCGH) analysis, we examined two patients with apparent chromosomal deletions in the distal 4q region. In the first, oaCGH identified a 2.441 megabase (Mb) duplication and a 12.651 Mb deletion at 4q34.1 in a pregnant female who transmitted this aberration to her son. This mother has only learning disabilities while her son had both renal and cardiac anomalies in the newborn period. Unrecognized paternal genetic factors may contribute to the variable expression. The second patient is a 17-year-old female with a history of Pierre Robin sequence, cardiac abnormalities and learning disabilities. She was diagnosed prenatally with a de novo 4q deletion, and oaCGH defined a 16.435 Mb deletion of 4q34.1-4q35.2. Phenotypic comparison and subtractive genomic mapping between these two cases suggested a 4 Mb region possibly harboring a candidate gene for Pierre Robin sequence. Our cases and review of reported cases with genomic findings indicated the presence of familial variants with variable expressivity as well as de novo or inherited pathogenic simple deletion, duplication and complex deletion and duplication in the distal 4q region.

LabCorp v. Metabolite Laboratories: The Supreme Court listens, but declines to speak.

In the United States, a longstanding legal rule exists against patenting natural phenomena. The Supreme Court recently had an opportunity to help define the boundaries and clarify the implications of this "natural phenomenon doctrine" in Laboratory Corporation of America v. Metabolite Labs., dismissed as improvidently granted. This article argues that the natural phenomenon doctrine renders both the patent claim at issue in LabCorp, and the patents that directly or indirectly claim biological correlations between genotypes and medical phenotypes, invalid or unenforceable under U.S. patent law.

Medical legal issues in prenatal diagnosis.

The capacity to diagnose fetal disease or abnormality continues to grow, especially in the genetic definition of the fetus. With this growth have come claims of medical malpractice that have mostly centered on a failure of informed consent. Failure may occur by omission or failed communication of pertinent information to the parents or by alleged error in the interpretation of diagnostic information. The usual claim against a physician or other provider is not that of causing damage or disease in the fetus but of causing a loss of opportunity to prevent conception or live birth of an infant who has an abnormality. Successful suits for "wrongful birth," brought by parents of an abnormal child, are common in many United States jurisdictions, but suits for "wrongful life," brought on behalf of the child, have usually been denied.

Late first-trimester placental disruption and subsequent gestational hypertension/preeclampsia.

OBJECTIVE: To evaluate the potential relationship between placental disruption in weeks 13 and 14 and the subsequent development of gestational hypertension or preeclampsia. METHODS: Using subjects recruited during a randomized trial funded by the National Institute of Child Health and Human Development, which compared early amniocentesis and late transabdominal chorionic villus sampling (CVS) in weeks 13 and 14, rates of gestational hypertension and preeclampsia were compared between cases with varying degrees of placental disruption. RESULTS: A total of 3,698 of 3,775 randomized subjects had cytogenetically normal pregnancies and were analyzed. A significantly higher rate of hypertension/preeclampsia was observed in the late CVS group (5.4%, n = 1,878) compared with the early amniocentesis cohort (3.5%, n = 1,820; P = .005). This difference persisted after controlling for maternal age, body mass index, parity, previous preterm delivery, smoking, and fetal gender. Early amniocentesis cases were further stratified on the basis of whether the placenta had been penetrated (n = 460) or not (n = 1,360). Risk of hypertensive complications was lowest if the placenta was not traversed (3.4%), greater with placental penetration (3.9%), and highest when the placenta was directly sampled during CVS (5.4%, P = .02). CONCLUSION: We hypothesize that focal disruption of the placenta at 13-14 weeks may increase the risk of hypertension/preeclampsia. These findings provide support for the theory that disturbances in early placentation lead subsequently to maternal hypertension.

The mid-trimester genetic sonogram.

The genetic sonogram is a composite algorithm combining multiple individual markers to increase Down syndrome risk prediction. Transformation of sonographic information into a standard mathematical format represented an early challenge that has now been surmounted. Using increasingly sophisticated mathematical techniques, individual patient risk can be estimated. High diagnostic accuracy comparable to standard mid-trimester serum algorithms has been reported. Most recently, a few studies have reported the ability to combine serum and biochemical markers to achieve diagnostic accuracy comparable to first-trimester screen. Even fewer studies have reported combinations of ultrasound and maternal urine markers. While it is clear that consistently high sensitivity and specificity for Down syndrome can be achieved, almost all the studies are based on high-risk groups. Studies in low-risk populations have suffered from lack of standardization. The relevance of genetic sonogram in a low-risk population thus remains to be proven. The most significant challenge, however, remains the development of uniform and reproducible sonographic and measurement standards. This is likely to be the most important factor in optimizing the accuracy of the mid-trimester genetic sonogram.

Pregnancy-associated plasma protein A, free beta-hCG, nuchal translucency, and risk of pregnancy loss.

OBJECTIVE: To estimate the likelihood of clinical early and late pregnancy loss as a function of first-trimester maternal serum analytes and fetal nuchal translucency measurements. METHODS: Study subjects were recruited for a National Institute of Child Health and Human Development-sponsored multicenter cohort study initially designed to study the detection of Down syndrome during the first trimester of pregnancy. The cohort consisted of women who had a live fetus between 10 and 14 weeks of gestation and had no significant vaginal bleeding. Women with prior fetal trisomy (T21/18) and those with structural or chromosomal abnormalities in the index pregnancy were excluded. First-trimester screening consisted of pregnancy-associated plasma protein A (PAPP-A), free beta-hCG, and nuchal translucency. Pregnancy loss rates in women with various levels of PAPP-A, free beta-hCG, or nuchal translucency (less than 1st, less than 5th, more than 95th, and more than 99th percentile) were compared with losses in women with normal values (5th to 95th percentile). RESULTS: The mean gestational age at screening of 7,932 women meeting study criteria was 12.1 weeks. Loss rates were only 0.36% at less than 20 weeks after normal free beta-hCG, PAPP-A, and nuchal translucency. Conversely, low levels of PAPP-A and free beta-hCG as well as increased nuchal translucency were individually associated with increased early loss. These associations persisted after controlling for maternal age and race using logistic regression analysis. CONCLUSION: Normal values of PAPP-A, free beta-hCG, and nuchal translucency are associated with a very low risk of pregnancy loss at less than 20 weeks.

Sequential pathways of testing after first-trimester screening for trisomy 21.

OBJECTIVE: To evaluate the performance and use of second-trimester multiple-marker maternal serum screening for trisomy 21 by women who had previously undergone first-trimester combined screening (nuchal translucency, pregnancy-associated plasma protein A, and free beta-hCG), with disclosure of risk estimates. METHODS: In a multicenter, first-trimester screening study sponsored by the National Institute of Child Health and Human Development, multiple-marker maternal serum screening with alpha-fetoprotein, unconjugated estriol, and total hCG was performed in 4,145 (7 with trisomy 21) of 7,392 (9 with trisomy 21) women who were first-trimester screen-negative and 180 (7 with trisomy 21) of 813 (52 with trisomy 21) who were first-trimester screen-positive. Second-trimester risks were calculated using multiples of the median and a standardized risk algorithm with a cutoff risk of 1:270. RESULTS: Among the first-trimester screen-negative cohort, 6 of 7 (86%) trisomy 21 cases were detected by second-trimester multiple-marker maternal serum screening with a false-positive rate of 8.9%. Among the first-trimester screen-positive cohort, all 7 trisomy 21 cases were also detected in the second trimester, albeit with a 38.7% false-positive rate. CONCLUSION: Our data demonstrate that a sequential screening program that provides patients with first-trimester results and offers the option for early invasive testing or additional serum screening in the second trimester can detect 98% of trisomy 21-affected pregnancies. However, such an approach will result in 17% of patients being considered at risk and, hence, potentially having an invasive test. LEVEL OF EVIDENCE: II-2

Combined serum and ultrasound screening for detection of fetal aneuploidy.

Experience gathered over the last decade from high-risk centers provide strong evidence that mid-trimester sonographic markers are sensitive for Down syndrome prediction. More recent data indicate that combining mid trimester sonography with traditional serum markers significantly improves diagnostic accuracy over either group of markers by themselves.

Variable expression of a novel PLP1 mutation in members of a family with Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease is a rare X-linked disorder caused by mutations of the proteolipid protein 1 gene that encodes a structural component of myelin. It is characterized by progressive psychomotor delay, nystagmus, spastic quadriplegia, and cerebellar ataxia. Variable clinical expression was seen in 5 members of a family bearing a novel missense mutation in proteolipid protein 1, c.619T>C. Symptomatic patients included a 6-year-old girl, her younger brother, and their maternal uncle, a 29-year-old college graduate initially diagnosed with cerebral palsy; their brain magnetic resonance imaging studies showed diffuse dysmyelination. The mother had a history of delayed walking, achieved independently by age 3; she and the maternal grandmother were asymptomatic on presentation. Review of clinical information and family history led to consideration of Pelizaeus-Merzbacher disease. Subsequent identification of the causal mutation enabled preimplantation genetic diagnosis and the birth of an unaffected child.

Proteomics: a novel methodology to complement prenatal diagnosis of chromosomal abnormalities and inherited human diseases.

The current revolution in biomedical sciences has raised new hope for early diagnosis, prevention, and treatment of human diseases. Recent advancements in genomics, proteomics, and other basic sciences are currently transforming the medical science, and offer the promise of answering many of the questions related to human diseases, including their early and accurate diagnosis. Profiling of biological fluids (i.e., serum, urine, amniotic fluid, and cerebrospinal fluid) has successfully identified relevant protein biomarkers that potentially can change early diagnosis and treatment of several medical conditions related to human pregnancy. Similarly, proteomics holds the promise to complement genomics to revolutionize screening and prenatal diagnosis of genetic conditions during early pregnancy. This article summarizes current technology and reviews the application of proteomics in diagnosis of genetic disorders during human pregnancy.

Fragile X syndrome carrier screening in the prenatal genetic counseling setting.

PURPOSE: To document our experience with fragile X carrier screening. METHODS: In this study, 29,103 women with no known or suspected family history of fragile X syndrome were offered fragile X carrier screening during their prenatal genetic counseling visit. Screening acceptance was analyzed by referral indication, carrier frequencies documented, and prenatal outcome data presented. RESULTS: Overall, 7.9% accepted carrier screening. The premutation frequency was 1 in 382, and the intermediate allele frequency was 1 in 143. CONCLUSIONS: Fragile X screening is a desirable option for some women seeking prenatal genetic counseling and should be made available to this population.

Elevated first-trimester nuchal translucency increases the risk of congenital heart defects.

OBJECTIVE: We sought to evaluate the association between first trimester nuchal translucency measurement and the risk for major congenital heart defect in chromosomally normal fetuses. STUDY DESIGN: First trimester (10 weeks 4 days of gestation to 13 weeks 6 days of gestation) nuchal translucency was obtained in a large prospective multicenter National Institute of Child Health and Human Development study for Down syndrome prediction. The study, which was conducted between May 1998 and December 2000, was restricted to singleton pregnancies. Gestational age was determined by crown rump length measurements. Perinatal outcomes were determined and included the frequency of major congenital heart defect, which was defined as those cases that potentially could require surgery, intensive medical therapy, or prolonged follow-up time. Logistic regression analysis was used to determine whether nuchal translucency was a significant predictor of congenital heart defect. RESULTS: There were 8167 chromosomally normal pregnancies, of which 21 cases of major congenital heart defect were identified at follow-up examination (incidence, 2.6/1000 pregnancies). The risk of congenital heart defect rose with increasing nuchal translucency measurements. The mean nuchal translucency value for the normal and congenital heart defect groups were 1.5 mm and 1.9 mm, respectively (P = .05). With a nuchal translucency measurement of < 2.0 mm, the incidence of congenital heart defect was 13 of 6757 pregnancies (1.9 of every 1000 pregnancies). At 2.0 to 2.4 mm, the incidence was 5 of 1032 pregnancies (4.8 of every 1000 pregnancies). At 2.5 to 3.4 mm, the incidence was 2 of 335 pregnancies (6.0 of every 1000 pregnancies). At > or = 3.5 mm, the incidence was 1 of 43 pregnancies (23 of every 1000 pregnancies). Logistic regression analysis confirmed that nuchal translucency was associated significantly with congenital heart defect (odds ratio, 2.1; 95% CI, 1.4-3.1; P = .0004). CONCLUSION: Increased first trimester nuchal translucency measurement was associated with a higher risk of major congenital heart defect in chromosomally normal pregnancies. The practical implications of our findings are that patients with unexplained elevations of nuchal translucency may need referral for a fetal echocardiogram.