Familial neonatal Marfan syndrome due to parental mosaicism of a missense mutation in the FBN1 gene

Reviewing hereditary connective tissue disorders: Proposals of harmonic medicolegal assessments

Hereditary connective tissue disorders (HCTDs) are a heterogeneous group of inherited diseases. These disorders show genetic mutations with loss of function of primary components of connective tissue, such as collagen and elastic fibers. There are more than 200 conditions that involve hereditary connective tissue disorders, while the most known are Marfan syndrome, Osteogenesis Imperfecta, and Ehlers-Danlos syndromes. These disorders need continuous updates, multidisciplinary skills, and specific methodologic evaluations sharing many medicolegal issues. Marfan syndrome and Ehlers-Danlos syndromes show a high risk of early sudden death. As a consequence of this, postmortem genetic testing can identify novel genotype-phenotype correlations which help the clinicians to assess personalized cardiovascular screening programs among the ill subjects. Genetic testing is also essential to identify children suffering from Osteogenesis Imperfecta, especially when a physical abuse is clinically suspected. However, this is a well-known clinical problem even though there are still challenges to interpret genetic data and variants of unknown significance due to the current extensive use of new genetic/genomic techniques. Additionally, the more significant applications and complexities of genomic testing raise novel responsibilities on the clinicians, geneticists, and forensic practitioners as well, increasing potential liability and medical malpractice claims. This systematic review provides a detailed overview on how multidisciplinary skills belonging to clinicians, medicolegal consultants, radiologists, and geneticists can cooperate to manage HCTDs from autopsy or clinical findings to genetic testing. Thus, technical aspects need to be addressed to the medicolegal community since there is no consensus works or guidelines which specifically discuss these issues.

Genotype-phenotype spectrum and prognosis of early-onset Marfan syndrome

BACKGROUND

Marfan syndrome is a genetic connective tissue disorder affecting skeletal, ocular, and cardiovascular organ systems. Previous research found that pathogenic variants clustered in exons 24-32 of fibrillin-1 (FBN1) gene result in more severe clinical phenotypes. Furthermore, genotype-phenotype correlation studies suggested that more severe cardiovascular phenotypes were related to variants held responsible for haploinsufficiency. Our objective was to analyze the differences in clinical manifestations and genotypes of individuals with early-onset Marfan syndrome and to assess their impact on management strategies.

METHODS

We analyzed clinical and genetic data of a new patient with early-onset Marfan syndrome together with 51 previously reported ones in the PubMed database between 1991 and 2022.

RESULTS

Analysis showed 94% (49/52) of pathogenic variants clustered in exons 24-32 of the FBN1. The most common skeletal features were arachnodactyly (98%), reduced elbow extension (48%), pectus deformity (40%), and scoliosis (39%). Haploinsufficiency variants were reported as having poor outcome in 87.5% of the cases. Among patients carrying variants that substitute a cysteine for another amino acid and those that do not change cysteine content, cardiac intervention was found to be associated with a better outcome (p = 0.035 vs. p = 0.002). Variants that create an extra cysteine residue were found to be associated with a higher risk of ectopia lentis. Additionally, children up to 36-months-old were more often reported as still alive at the time of publication compared to newborns (p < 0.01).

CONCLUSIONS

Our findings have implications for prognosis, because different genotype groups and their resulting phenotype may require personalized care and management.

A unique cardiovascular presentation of Marfan syndrome

We report a neonate with severe Marfan syndrome (MS), prenatally identified to have persistent atrial tachycardia, biventricular dysfunction, and an unusual structure within the atria. Detailed postnatal echocardiographic evaluation and cross-sectional imaging confirmed congenital pseudoaneurysm of the mitral-aortic intervalvular fibrosa. Emergent testing by next-generation sequencing identified a FBN1 pathological variant, key to establishing goals of care. To our knowledge, this is the first reported case of a congenital pseudoaneurysm of the mitral-aortic intervalvular fibrosa in MS.

Detection of Very Low-Level Somatic Mosaic COL4A5 Splicing Variant in Asymptomatic Female Using Droplet Digital PCR

Background

Alport syndrome is a hereditary glomerulopathy featured by haematuria, proteinuria, and progressive renal failure. X-linked Alport syndrome (XLAS) due to COL4A5 disease-causing variants is the most common form. In the case of XLAS resulting from 10–18% presumed de novo COL4A5 disease-causing variants, there are only a few studies for mosaicism in the probands or parents. Very low-level (<1.0%) somatic mosaicism for COL4A5 disease-causing variants has not been published.

Materials and Methods

Chinese XLAS families with suspected parental mosaicism were enrolled in the present study to evaluate the forms of mosaicism, to offer more appropriate genetic counseling. PCR and direct sequencing were used to detect COL4A5 disease-causing variants harbored by the affected probands in parental multi-tissue DNAs (peripheral blood, urine sediments, saliva, hair), and droplet digital PCR (ddPCR) was used to quantify the mutant COL4A5 allelic fractions in parental different samples such as peripheral blood, saliva, and urine sediments.

Results

A Chinese asymptomatic female with suspected somatic and germline mosaicism was enrolled in the present study. She gave birth to two boys with XLAS caused by a hemizygous disease-causing variant c. 2245-1G>A in COL4A5 (NM_033380) intron 28, whereas this disease-causing variant was not detected in genomic DNA extracted from peripheral blood leukocytes in the woman using Sanger sequencing. She had multiple normal urine test results, and continuous linear immunofluorescence staining of α2 (IV) and α5 (IV) chains of skin tissue. Sanger sequencing demonstrated that COL4A5 disease-causing variant c. 2245-1G>A was not detected in her genomic DNAs isolated from urine sediments, saliva, and hair roots. Using ddPCR, the wild-type and mutant-type (c.2245-1G>A) COL4A5 was identified in the female's genomic DNAs isolated from peripheral blood, saliva, and urine sediments. The mutant allelic fractions in these tissues were 0.26% (peripheral blood), 0.73% (saliva), and 1.39% (urine), respectively.

Conclusions

Germline and very low-level somatic mosaicism for a COL4A5 splicing variant was detected in an asymptomatic female, which highlights that parental mosaicism should be excluded when a COL4A5 presumed de novo disease-causing variant is detected.

Symptomatic mosaicism for a novel FBN1 splice site variant in a parent causing inherited neonatal Marfan syndrome

Neonatal Marfan syndrome is a severe, early onset presentation of pathogenic variants in FBN1. Because of the significant cardiac involvement and early mortality, nearly all reported cases have been de novo, and the disorder has not been documented to be inherited from a symptomatic parent. Here, we present a female infant with neonatal Marfan syndrome who was born to a father with Marfan syndrome. Prior to the birth of his daughter, the father had been found to have an FBN1 missense variant of uncertain clinical significance. Initial familial variant testing of the infant did not reveal the same missense variant, but Sanger sequencing of FBN1 subsequently identified a pathogenic splice site variant. The father was then found to have 10%-20% mosaicism for the same splice site variant.

Parental mosaicism in Marfan and Ehlers-Danlos syndromes and related disorders

Marfan syndrome (MFS) is a heritable connective tissue disorder (HCTD) caused by pathogenic variants in FBN1 that frequently occur de novo. Although individuals with somatogonadal mosaicisms have been reported with respect to MFS and other HCTD, the overall frequency of parental mosaicism in this pathology is unknown. In an attempt to estimate this frequency, we reviewed all the 333 patients with a disease-causing variant in FBN1. We then used direct sequencing, combined with High Resolution Melting Analysis, to detect mosaicism in their parents, complemented by NGS when a mosaicism was objectivized. We found that (1) the number of apparently de novo events is much higher than the classically admitted number (around 50% of patients and not 25% as expected for FBN1) and (2) around 5% of the FBN1 disease-causing variants were not actually de novo as anticipated, but inherited in a context of somatogonadal mosaicisms revealed in parents from three families. High Resolution Melting Analysis and NGS were more efficient at detecting and evaluating the level of mosaicism compared to direct Sanger sequencing. We also investigated individuals with a causal variant in another gene identified through our "aortic diseases genes" NGS panel and report, for the first time, on an individual with a somatogonadal mosaicism in COL5A1. Our study shows that parental mosaicism is not that rare in Marfan syndrome and should be investigated with appropriate methods given its implications in patient's management.

A systematic study and literature review of parental somatic mosaicism of FBN1 pathogenic variants in Marfan syndrome

BACKGROUND

A proportion of de novo variants in patients affected by genetic disorders, particularly those with autosomal dominant (AD) inheritance, could be the consequence of somatic mosaicism in one of the progenitors. There is growing evidence that germline and somatic mosaicism are more common and play a greater role in genetic disorders than previously acknowledged. In Marfan syndrome (MFS), caused by pathogenic variants in the fibrillin-1 gene (FBN1) gene, approximately 25% of the disease-causing variants are reported as de novo. Only a few cases of parental mosaicism have been reported in MFS.

METHODS

Employing an amplicon-based deep sequencing (ADS) method, we carried out a systematic analysis of 60 parents of 30 FBN1 positive, consecutive patients with MFS with an apparently de novo pathogenic variant.

RESULTS

Out of the 60 parents studied (30 families), the majority (n=51, 85%) had a systemic score of 0, seven had a score of 1 and two a score of 2, all due to minor criteria common in the normal population. We detected two families with somatic mosaicism in one of the progenitors, with a rate of 6.6% (2/30) of apparently de novo cases.

CONCLUSIONS

The search for parental somatic mosaicism should be routinely implemented in de novo cases of MFS, to offer appropriate genetic and reproductive counselling as well as to reveal masked, isolated clinical signs of MFS in progenitors that may require specific follow-up.

Assembly assay identifies a critical region of human fibrillin-1 required for 10-12 nm diameter microfibril biogenesis

The human FBN1 gene encodes fibrillin-1 (FBN1); the main component of the 10–12 nm diameter extracellular matrix microfibrils. Marfan syndrome (MFS) is a common inherited connective tissue disorder, caused by FBN1 mutations. It features a wide spectrum of disease severity, from mild cases to the lethal neonatal form (nMFS), that is yet to be explained at the molecular level. Mutations associated with nMFS generally affect a region of FBN1 between domains TB3-cbEGF18—the "neonatal region". To gain insight into the process of fibril assembly and increase our understanding of the mechanisms determining disease severity in MFS, we compared the secretion and assembly properties of FBN1 variants containing nMFS-associated substitutions with variants associated with milder, classical MFS (cMFS). In the majority of cases, both nMFS- and cMFS-associated neonatal region variants were secreted at levels comparable to wild type. Microfibril incorporation by the nMFS variants was greatly reduced or absent compared to the cMFS forms, however, suggesting that nMFS substitutions disrupt a previously undefined site of microfibril assembly. Additional analysis of a domain deletion variant caused by exon skipping also indicates that register in the neonatal region is likely to be critical for assembly. These data demonstrate for the first time new requirements for microfibril biogenesis and identify at least two distinct molecular mechanisms associated with disease substitutions in the TB3-cbEGF18 region; incorporation of mutant FBN1 into microfibrils changing their integral properties (cMFS) or the blocking of wild type FBN1 assembly by mutant molecules that prevents late-stage lateral assembly (nMFS).

MosaicBase: A Knowledgebase of Postzygotic Mosaic Variants in Noncancer Disease-related and Healthy Human Individuals

Mosaic variants resulting from postzygotic mutations are prevalent in the human genome and play important roles in human diseases. However, except for cancer-related variants, there is no collection of postzygotic mosaic variants in noncancer disease-related and healthy individuals. Here, we present MosaicBase, a comprehensive database that includes 6698 mosaic variants related to 266 noncancer diseases and 27,991 mosaic variants identified in 422 healthy individuals. Genomic and phenotypic information of each variant was manually extracted and curated from 383 publications. MosaicBase supports the query of variants with Online Mendelian Inheritance in Man (OMIM) entries, genomic coordinates, gene symbols, or Entrez IDs. We also provide an integrated genome browser for users to easily access mosaic variants and their related annotations for any genomic region. By analyzing the variants collected in MosaicBase, we find that mosaic variants that directly contribute to disease phenotype show features distinct from those of variants in individuals with mild or no phenotypes, in terms of their genomic distribution, mutation signatures, and fraction of mutant cells. MosaicBase will not only assist clinicians in genetic counseling and diagnosis but also provide a useful resource to understand the genomic baseline of postzygotic mutations in the general human population. MosaicBase is publicly available at http://mosaicbase.com/ or http://49.4.21.8:8000.

Extracellular matrix dynamics in vascular remodeling

Vascular remodeling is the adaptive response to various physiological and pathophysiological alterations that are closely related to aging and vascular diseases. Understanding the mechanistic regulation of vascular remodeling may be favorable for discovering potential therapeutic targets and strategies. The extracellular matrix (ECM), including matrix proteins and their degradative metalloproteases, serves as the main component of the microenvironment and exhibits dynamic changes during vascular remodeling. This process involves mainly the altered composition of matrix proteins, metalloprotease-mediated degradation, posttranslational modification of ECM proteins, and altered topographical features of the ECM. To date, adequate studies have demonstrated that ECM dynamics also play a critical role in vascular remodeling in various diseases. Here, we review these related studies, summarize how ECM dynamics control vascular remodeling, and further indicate potential diagnostic biomarkers and therapeutic targets in the ECM for corresponding vascular diseases.

Detection of ten novel FBN1 mutations in Chinese patients with typical or incomplete Marfan syndrome and an overview of the genotype-phenotype correlations

OBJECTIVE

The aim of this study is to identify the mutation spectrum of FBN1 in patients with Marfan syndrome (MFS) or Marfan-Like Phenotypes and to analyze the genotype-phenotype correlations of existing literature.

METHODS AND RESULTS

A total of 21 unrelated patients with a definite or suspected clinical diagnosis of MFS were recruited for research. Eleven FBN1 mutations were identified in 12 patients who strictly fulfilled the Ghent criteria for MFS, and 1 FBN1 mutations were detected in 9 patients with suspected MFS by screening the mutations of FBN1. These FBN1 mutations include 10 novel mutations (c.357 C>A, c.493 C>T, c.1374 T>A, c.4143 delG, c. 6987 C>G, c.7238 G>A, c. 7765 A>G, c.8200 A>G, c. 8431 G>A, c.8547 T>G,) and 2 previously reported mutations (c.4567 C>T, c.4615 C>T). By searching PubMed and Embase (from 1990 up to December 2018), twenty nine studies (including the present study) with 890 subjects with MFS or Marfan-like phenotypes were included to analyze the genotype-phenotype correlations. Several genotype-phenotype correlations were founded. Firstly, mutations of premature termination codons (PTC) were associated with an increased risk of major cardiovascular involvements. Secondly, the frequency of patients with major cardiovascular involvement in exons 43-65 group was as high as that in exons 24-32 group (71.4% vs. 77.0%; p = 0.238). Finally, cysteine missense mutations might be associated with major cardiovascular involvements.

CONCLUSIONS

These results extended the FBN1 mutation spectrum of this rare disease and revealed the genotype-phenotype correlations in MFS by analyzing existing literature.

Perinatal diagnosis and management of early-onset Marfan syndrome: case report and systematic review

Early onset Marfan syndrome is the most severe form of Marfan syndrome diagnosed during perinatal period. Early onset Marfan syndrome is associated with high mortality rates, usually within the first 2 years of life. First, we present a case of prenatally diagnosed early onset Marfan syndrome in a dichorionic diamniotic twin pregnancy, where suspicion was raised at 35 weeks of gestation. Ultrasound and fetal magnetic resonance imaging were used to assess prenatal findings in the affected fetus. She presented right diaphragmatic eventration, elongation of humerus and femur and subluxation of the crystalline lens. She died 3 months after birth. Secondly, we present a PubMed-based review of the published articles on early onset Marfan syndrome, with pre- or postnatal suspicion or diagnosis. We found 39 articles published between 1981 and 2017, arising information on 55 cases. Including ours, early onset Marfan syndrome was prenatally diagnosed in 34.54% of the cases. In these cases, the most frequent prenatal findings were cardiomegaly, dilatation of the great vessels and mitral or tricuspid regurgitation. Mortality rate during the first 15 months after birth was 73.68%. In the postnatally diagnosed cases, the most frequent findings were arachnodactyly, dilatation of the great vessels and mitral or tricuspid regurgitation. Mortality rate was 61.11%. Overall genetic confirmation was performed in 67.27% of the cases. Prenatal diagnosis of early onset Marfan syndrome is challenging but of utmost importance, since management should take place in a tertiary care center, by a multidisciplinary team. Differential diagnosis is essential in order to perform an adequate genetic counseling.

Novel Marfan Syndrome-Associated Mutation in the FBN1 Gene Caused by Parental Mosaicism and Leading to Abnormal Limb Patterning

Marfan syndrome is an autosomal dominant disorder of the connective tissue caused by mutations in the fibrillin-1 (FBN1) gene. Mutations affecting cysteine residues within the epidermal growith factor-like calcium-binding domains (EGF_CA) of FBN1 are associated with Marfan syndrome features and, especially, with ectopia lentis. We report a novel substitution, affecting the first cysteine of an EGF_CA-binding module encoded by exon 63 of FBN1 (C2571Y), in a patient presenting with typical Marfan syndrome features but without ectopia lentis. The involvement of this particular carboxi-terminal domain in bone morphogenetic protein signaling is evidenced by patterning defects in the apendicular skeleton shown by the gain of a phalange at digit 1 and the fusion of some wrist bones. Although the mutation appeared as sporadic, detailed analysis revealed that the asymptomatic father was a gonosomal mosaic, and that aproximately 25% of his body cells carry the mutation. Based on this and previous evidence on the origin of sporadic mutations, we would like to stress the importance of detailed parental genetic screening, so the risk of recurrence may be evaluated.

Marfan syndrome associated aortic disease in neonates and children: a clinical-morphologic review

BACKGROUND

Marfan syndrome (MFS) is a multisystem connective tissue disorder that can lead to aortic dilation requiring aortic root replacement. Neonatal MFS (nMFS) is a rare and severe form of MFS compared to classic MFS (cMFS). Aortic root histology in MFS is thought to demonstrate predominantly medial degeneration (MD) of a translamellar mucoid extracellular matrix accumulation (MEMA-T) vs. the intralamellar mucoid extracellular matrix accumulation (MEMA-I) seen in other aortopathies. The objective of this study was to describe the clinical and histopathologic features of nMFS and cMFS patients undergoing aortic root replacement.

METHODS

Children with MFS who underwent aortic root replacement between 2000 and 2012 at a single institution were included. Medical records including clinical details, aortic dimensions (Z scores), and histology including MD type were obtained. Statistics were descriptive with univariate analysis of age at surgery and type of MD.

RESULTS

Eleven patients, 3 (27%) with nMFS, were included. Root dilation at time of surgery was greater in nMFS compared to cMFS (Z=12.8 vs. 7.6, P=.005), and nMFS patients were younger at time of surgery (7.3 vs. 18.8 years, P=.002). Histology in the nMFS group demonstrated MEMA-I in one and no MD in two. In the cMFS group, there were three with MEMA-T, four with MEMA-I, and one with both types.

CONCLUSION

In summary, nMFS has earlier root dilation often in the absence of MD. Both forms of MD were present in our cohort, and there was no correlation between age at surgery and type of MD.

FBN1: The disease-causing gene for Marfan syndrome and other genetic disorders

FBN1 encodes the gene for fibrillin-1, a structural macromolecule that polymerizes into microfibrils. Fibrillin microfibrils are morphologically distinctive fibrils, present in all connective tissues and assembled into tissue-specific architectural frameworks. FBN1 is the causative gene for Marfan syndrome, an inherited disorder of connective tissue whose major features include tall stature and arachnodactyly, ectopia lentis, and thoracic aortic aneurysm and dissection. More than one thousand individual mutations in FBN1 are associated with Marfan syndrome, making genotype-phenotype correlations difficult. Moreover, mutations in specific regions of FBN1 can result in the opposite features of short stature and brachydactyly characteristic of Weill-Marchesani syndrome and other acromelic dysplasias. How can mutations in one molecule result in disparate clinical syndromes? Current concepts of the fibrillinopathies require an appreciation of tissue-specific fibrillin microfibril microenvironments and the collaborative relationship between the structures of fibrillin microfibril networks and biological functions such as regulation of growth factor signaling.

A Case Based Approach to Clinical Genetics of Thoracic Aortic Aneurysm/Dissection

Thoracic aortic aneurysm/dissection (TAAD) is a potential lethal condition with a rising incidence. This condition may occur sporadically; nevertheless, it displays familial clustering in >20% of the cases. Family history confers a six- to twentyfold increased risk of TAAD and has to be considered in the identification and evaluation of patients needing an adequate clinical follow-up. Familial TAAD recognizes a number of potential etiologies with a significant genetic heterogeneity, in either syndromic or nonsyndromic forms of the manifestation. The clinical impact and the management of patients with TAAD differ according to the syndromic and nonsyndromic forms of the manifestation. The clinical management of TAAD patients varies, depending on the different forms. Starting from the description of patient history, in this paper, we summarized the state of the art concerning assessment of clinical/genetic profile and therapeutic management of TAAD patients.

Neonatal Marfan Syndrome: Report of a Case with an Inherited Splicing Mutation outside the Neonatal Domain

We report a child and her mother affected by Marfan syndrome. The child presented with a phenotype of neonatal Marfan syndrome, revealed by acute and refractory heart failure, finally leading to death within the first 4 months of life. Her mother had a common clinical presentation. Genetic analysis revealed an inherited FBN1 mutation. This intronic mutation (c.6163+3_6163+6del), undescribed to date, leads to exon 49 skipping, corresponding to in-frame deletion of 42 amino acids (p.Ile2014_Asp2055del). FBN1 next-generation sequencing did not show any argument for mosaicism. Association in the same family of severe neonatal and classical Marfan syndrome illustrates the intrafamilial phenotype variability.

Early onset marfan syndrome: Atypical clinical presentation of two cases

Early onset Marfan Syndrome (eoMFS) is a rare, severe form of Marfan Syndrome (MFS). The disease has a poor prognosis and most patients present with resistance to heart failure treatment during the newborn period. This report presents two cases of eoMFS with similar clinical features diagnosed in the newborn period and who died at an early age due to the complications related to the involvement of the cardiovascular system.

Advanced Paternal Age and Risk of Musculoskeletal Congenital Anomalies in Offspring

OBJECTIVE

Previous research suggests that advanced paternal age increases the risk of musculoskeletal congenital anomalies (CAs) in offspring, but findings are inconsistent. This study aims to investigate the risk of musculoskeletal CAs according to paternal age at birth in an unselected population covering cohort of children.

STUDY DESIGN

A register-based prospective study of 1,605,885 children born in Denmark, 1978-2004, using information from record-linked health and administrative registers. The association between paternal age and overall musculoskeletal CAs, limb anomalies, craniosynostosis, skeletal dysplasias, syndromic musculoskeletal CAs, and other musculoskeletal CAs were investigated by multiple logistic regression analysis.

RESULTS

For overall musculoskeletal CAs, a slightly higher risk per 10-year increase in paternal age was found (odds ratio [OR] = 1.06 [95% CI: 1.01-1.11; where CI is confidence interval]). A 26% (95% CI: 2-56%) excess risk was found for fathers aged 50+ years compared to fathers aged 30-34 years. For syndromic musculoskeletal CAs, excess risks were found for fathers aged 40+ years, compared to fathers aged 30-34 years (40-44: OR = 1.38 [95% CI: 1.01-1.88], 45-49: OR = 1.45 [95% CI: 0.89-2.34], 50+: OR = 1.42 [95% CI: 0.73-2.79]). The risks in all other subgroups of musculoskeletal CAs were increased for fathers aged 50+ years.

CONCLUSIONS

A slightly higher risk for overall musculoskeletal CAs in offspring was found with increasing paternal age, mainly due to an excess risk of syndromic musculoskeletal CAs for fathers aged 40+ years. While associations between paternal age 50+ years and increased risk of all subtypes of musculoskeletal CAs were indicated, advanced paternal age likely plays a minor role in the etiology of these anomalies.

Amplicon Resequencing Identified Parental Mosaicism for Approximately 10% of "de novo" SCN1A Mutations in Children with Dravet Syndrome

The majority of children with Dravet syndrome (DS) are caused by de novo SCN1A mutations. To investigate the origin of the mutations, we developed and applied a new method that combined deep amplicon resequencing with a Bayesian model to detect and quantify allelic fractions with improved sensitivity. Of 174 SCN1A mutations in DS probands which were considered "de novo" by Sanger sequencing, we identified 15 cases (8.6%) of parental mosaicism. We identified another five cases of parental mosaicism that were also detectable by Sanger sequencing. Fraction of mutant alleles in the 20 cases of parental mosaicism ranged from 1.1% to 32.6%. Thirteen (65% of 20) mutations originated paternally and seven (35% of 20) maternally. Twelve (60% of 20) mosaic parents did not have any epileptic symptoms. Their mutant allelic fractions were significantly lower than those in mosaic parents with epileptic symptoms (P = 0.016). We identified mosaicism with varied allelic fractions in blood, saliva, urine, hair follicle, oral epithelium, and semen, demonstrating that postzygotic mutations could affect multiple somatic cells as well as germ cells. Our results suggest that more sensitive tools for detecting low-level mosaicism in parents of families with seemingly "de novo" mutations will allow for better informed genetic counseling.

Recognizable syndromes in the newborn period

Making the diagnosis of genetic syndromes in the neonatal period can be challenging, as limited information concerning growth and development is available. The pattern of dysmorphic features and malformations is, therefore, correspondingly more important in syndrome recognition. The authors provide specific examples of the differences in the presentation for selected syndromes between the newborn period and later childhood. The purpose is to describe the variation in presentation that can occur with chronologic age and to aid in the early diagnosis of these conditions.

Paternal fibrillin-1 mutation transmitted to an affected son with neonatal marfan syndrome: the importance of early recognition

We describe a case of neonatal Marfan syndrome diagnosed because of a family history, dysmorphic features, and cardiac abnormality. The echocardiogram showed aortic root dilatation. Molecular genetic studies showed a mutation in exon 31 of the FBN1 gene in the infant and father. The infant was treated with losartan, which significantly slowed the rate of enlargement of the aorta.

Genetic susceptibility

Why only 20% of smokers develop clinically relevant chronic obstructive pulmonary disease (COPD) was a puzzle for many years. Now, epidemiologic studies point clearly toward a large heritable component. The combination of genome-wide association studies and candidate gene analysis is helping to identify those genetic variants responsible for an individual's susceptibility to developing COPD. In this review, the current data implicating specific loci and genes in the pathogenesis of COPD are examined.

Health supervision for children with Marfan syndrome

Marfan syndrome is a systemic, heritable connective tissue disorder that affects many different organ systems and is best managed by using a multidisciplinary approach. The guidance in this report is designed to assist the pediatrician in recognizing the features of Marfan syndrome as well as caring for the individual with this disorder.

Dilatation of the great arteries in an infant with marfan syndrome and ventricular septal defect

We describe an infant presenting with contractures of the fingers, a large ventricular septal defect (VSD), and severe pulmonary artery dilatation. He had clinical and echocardiographic features of both neonatal or infantile Marfan syndrome (MFS) and congenital contractural arachnodactyly. After surgical VSD closure, the aortic root developed progressive dilatation while the size of pulmonary artery returned to normal limits. Eventually the diagnosis of MFS was confirmed by DNA analysis.

Prognosis factors in probands with an FBN1 mutation diagnosed before the age of 1 year

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder. Diagnostic criteria of neonatal MFS (nMFS), the most severe form, are still debated. The aim of our study was to search for clinical and molecular prognostic factors that could be associated with length of survival. Probands ascertained via the framework of the Universal Marfan database-FBN1, diagnosed before the age of 1 y and presenting with cardiovascular features (aortic root dilatation or valvular insufficiency) were included in this study. Clinical and molecular data were correlated to survival. Among the 60 individuals, 38 had died, 82% died before the age of 1 y, mostly because of congestive heart failure. Three probands reached adulthood. Valvular insufficiencies and diaphragmatic hernia were predictive of shorter life expectancy. Two FBN1 mutations were found outside of the exon 24-32 region (in exons 4 and 21). Mutations in exons 25-26 were overrepresented and were associated with shorter survival (p = 0.03). We report the largest genotyped series of probands with MFS diagnosed before 1 y of life. In this population, factors significantly associated with shorter survival are presence of valvular insufficiencies or diaphragmatic hernia in addition to a mutation in exons 25 or 26.

Severe Marfan syndrome due to FBN1 exon deletions

Marfan syndrome is an autosomal dominant condition, with manifestations mainly in the skeletal, ocular, and cardiovascular systems. The disorder is caused by mutations in fibrillin-1 gene (FBN1). The majority of these are family-specific point mutations, with a small number being predicted to cause exon-skipping. To date, there have only been five reports of in-frame exon deletions in FBN1, with the largest of these spanning three exons. Mosaicism is rarely recorded and has only been reported in the unaffected, or mildly affected, parents of probands. Here, we report on the clinical histories of two children with exon deletions in FBN1. Both have severe Marfan syndrome with significant signs in infancy. One patient has a deletion of exon 33, which has not previously been reported. The other has the largest reported deletion, which spans 37 exons, and also represents the first reported case of mosaicism in a patient with Marfan syndrome.