Human chromosome map of lymphedema-lymphangiogenesis genes: Template for current and future discovery.

We have created a human chromosomal map of the location of known and candidate genes involved in primary lymphedema (PLE). This should facilitate further discovery and provide a basis for understanding microdeletions which cause lymphedema.

Prevalence of pathogenic variants and variants of unknown significance in patients at high risk of breast cancer: A systematic review and meta-analysis of gene-panel data.

BACKGROUND: Gene-panels are used to assess predisposition to breast cancer by simultaneous testing of multiple susceptibility genes. This approach increases the identification of variants of unknown significance (VUS) that cannot be used in clinical decision-making. We performed a systematic review of published studies to calculate the prevalence of VUS and pathogenic variants (PV) in routinely tested breast cancer susceptibility genes in patients at high risk of breast cancer. METHODS: We comprehensively searched the literature using Medline through May 23, 2017 for studies conducting gene-panel testing on germline DNA of women with familial breast cancer and reporting on both PVs and VUSs. A meta-analysis of the collected data was carried out to obtain pooled VUS and PV prevalence estimates per gene using a generalized linear mixed model with logit link for binomial distribution. RESULTS: Of 602 publications, 4 were eligible and included 1870 patients. The panels encompassed 4-27 considered genes. Overall, the estimated probability per gene of a PV and VUS was 55% (95% confidence interval (CI) 26%-81%) and 91% (95% CI 78%-97%), respectively (p = 0.0066). The estimated probability per patient of a PV and VUS was 8% (95% CI 1%-34%) and 23% (95% CI 7%-52%), respectively (p = 0.0052). The ratio of VUS to PV was highest in the mismatch repair genes MLH1, MSH2, MSH6, PMS2 (18.7), CDH1 (13.4) and ATM (9.5). Amongst the 1468 patients tested for BRCA1 and BRCA2, only these two genes had a VUS to PV ratio of less than one (0.2 and 0.6, respectively). CONCLUSION: With the current panels, the probability of detecting a VUS is significantly higher than the probability of detecting a PV. Better classification of VUSs is therefore critical and requires gene-specific VUS-assessment in every future study of gene-panel testing in patients at high risk of breast cancer.

Tandem inversion duplication within F8 Intron 1 associated with mild haemophilia A.

In approximately 90% of mild haemophilia A (HA) patients, a missense mutation can be identified using complete gene sequencing. In this study, multiplex ligation-dependent probe amplification analysis was performed as a second step in 10 French-speaking Belgian with mild HA presenting no detectable causal mutation by complete sequencing of the factor VIII (FVIII) (F8) gene's 26 exons and its 1.2 kb of contiguous promoter sequence. This gene dosage technique enabled the detection of exon 1 duplications of F8 in three apparently unrelated subjects. Using array-comparative genomic hybridization, breakpoint analysis delimited the duplication extent to 210 kb in the F8 intron 1 and VBP1 gene intragenic position. We postulated that the rearrangement responsible for this duplication, never before reported, could be attributed to a symmetrical tandem inversion duplication, resulting in a large 233 kb rearrangement of F8 intron 1. This rearranged intron should lead to the production of a small number of normal mRNA transcripts in relation to the mild HA phenotype. Our analysis of the entire F8 mRNA from index case 1, particularly the segment containing exons 1-9, revealed normal amplification and sequencing. Reduced plasma FVIII antigen levels caused by cross-reacting material is associated with a quantitative deficiency of plasma FVIII. Male patients were unresponsive to desmopressin (1-deamino-8-D-arginine vasopressin). All patients displayed identical F8 haplotypes, despite not being related, which suggests a possible founder effect caused by a 210 kb duplication involving F8 exon 1.

Overrepresentation of missense mutations in mild hemophilia A patients from Belgium: founder effect or independent occurrence?

Roughly 40% of observed mutations responsible for hemophilia A (HA) are novel and present in either a single family or a limited number of unrelated families. During routine diagnostic analysis of 73 unrelated Belgian patients with mild HA, 4 out of 43 different mutations (p.Ser2030Asn, p.Arg2178Cys, p.Arg2178His, and p.Pro2311His) were detected in more than one family, representing 35% of total identified mutations. To discriminate between an independent recurrence or a founder effect, an analysis of intra- and -extragenic single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs) flanking the F8 gene was conducted. SNP haplotype and microsatellite analysis revealed strong evidence that p.Ser2030Asn and p.Pro2311His mutations were probably associated with a founder effect. The two other mutations localized in an F8 cytosine-phosphate-guanine (CpG) site likely resulted from recurrent de novo events. This study suggests that missense mutations producing C-to-T or G-to-A substitutions in CpG dinucleotide can occur de novo with more repetition than other causal substitutions that do not affect the CpG site. Analysis of F8 database implied that CpG sites throughout the F8 gene are not all mutated with the same frequency. Causes are still unknown and remain to be identified.

Antenatal presentation of hereditary lymphedema type I.

Fetal edema can present as limited subcutaneous edema, fluid accumulation in body cavities or hydrops fetalis. Hydrops fetalis is the end stage of a variety of fetal/maternal disorders and nonimmune etiology represents more than 3/4 of cases. Lymphatic dysplasia may account for a subset of patients with nonimmune and "idiopathic" hydrops fetalis, fetal chylous ascites or chylothorax. We present two unrelated patients with antenatal features of hereditary lymphedema syndrome, in whom Milroy disease was diagnosed after birth. At least, 20 genes have been identified to cause primary lymphedema, with sometimes antenatal features. Hereditary lymphedema syndrome should be considered in cases of nonimmune hydrops fetalis/fetal edema after ruling out the more common etiologies.

Hypotrichosis-lymphedema-telangiectasia-renal defect associated with a truncating mutation in the SOX18 gene.

SOX18 mutations in humans are associated with both recessive and dominant hypotrichosis-lymphedema-telangiectasia syndrome (HLTS). We report two families with affected children carrying a SOX18 mutation: a living patient and his stillborn brother from Canada and a Belgian patient. The two living patients were diagnosed with HLTS and DNA analysis for the SOX18 gene showed that both had the identical heterozygous C > A transversion, resulting in a pre-mature truncation of the protein, lacking the transactivation domain. Both living patients developed renal failure with severe hypertension in childhood for which both underwent renal transplantation. To our best knowledge this is the first report of renal failure associated with heterozygous mutations in the SOX18 gene. We conclude that this specific mutation results in a new, autosomal dominant condition and propose the acronym HLT-renal defect syndrome for HLTRS.

Mutations in the VEGFR3 signaling pathway explain 36% of familial lymphedema.

Lymphedema is caused by dysfunction of lymphatic vessels, leading to disabling swelling that occurs mostly on the extremities. Lymphedema can be either primary (congenital) or secondary (acquired). Familial primary lymphedema commonly segregates in an autosomal dominant or recessive manner. It can also occur in combination with other clinical features. Nine mutated genes have been identified in different isolated or syndromic forms of lymphedema. However, the prevalence of primary lymphedema that can be explained by these genetic alterations is unknown. In this study, we investigated 7 of these putative genes. We screened 78 index patients from families with inherited lymphedema for mutations in FLT4, GJC2, FOXC2, SOX18, GATA2, CCBE1, and PTPN14. Altogether, we discovered 28 mutations explaining 36% of the cases. Additionally, 149 patients with sporadic primary lymphedema were screened for FLT4, FOXC2, SOX18, CCBE1, and PTPN14. Twelve mutations were found that explain 8% of the cases. Still unidentified is the genetic cause of primary lymphedema in 64% of patients with a family history and 92% of sporadic cases. Identification of those genes is important for understanding of etiopathogenesis, stratification of treatments and generation of disease models. Interestingly, most of the proteins that are encoded by the genes mutated in primary lymphedema seem to act in a single functional pathway involving VEGFR3 signaling. This underscores the important role this pathway plays in lymphatic development and function and suggests that the unknown genes also have a role.

Síndrome malformaciones capilares-malformaciones arteriovenosas: presentación de 2 casos, claves diagnósticas y manejo / Capillary Malformation-Arteriovenous Malformation Syndrome: A Report of 2 Cases, Diagnostic Criteria, and Management

El síndrome malformaciones capilares-malformaciones arteriovenosas es un tipo de malformación vascular poco frecuente que se describió en 2003. Se hereda de forma autosómica dominante, y se ha objetivado que está causado por mutaciones heterocigotas en el gen RASA1, que codifica la proteína RASp21. Dicho síndrome se caracteriza por malformaciones capilares pequeñas y múltiples que se asocian con malformaciones arteriovenosas o fístulas arteriovenosas, tanto en los individuos afectos como en sus familias. Describimos aquí 2 nuevos casos familiares de este síndrome que hemos diagnosticado y estudiado en nuestro centro, tanto desde el punto de vista clínico como genético (AU)

Capillary malformation-arteriovenous malformation syndrome is a rare type of vascular malformation first described in 2003. It is an autosomal dominant inherited disorder that has been reported in association with heterozygous mutations in the RASA1 gene, which encodes the protein RASp21. The clinical picture is characterized by multiple small capillary malformations which are associated with either arteriovenous malformations or arteriovenous fistulas in both the affected individual and other members of their family. We describe 2 new familial cases of this syndrome that were clinically and genetically diagnosed and studied in our hospital (AU)

Capillary malformation-arteriovenous malformation syndrome: a report of 2 cases, diagnostic criteria, and management.

Capillary malformation-arteriovenous malformation syndrome is a rare type of vascular malformation first described in 2003. It is an autosomal dominant inherited disorder that has been reported in association with heterozygous mutations in the RASA1 gene, which encodes the protein RASp21. The clinical picture is characterized by multiple small capillary malformations which are associated with either arteriovenous malformations or arteriovenous fistulas in both the affected individual and other members of their family. We describe 2 new familial cases of this syndrome that were clinically and genetically diagnosed and studied in our hospital.

Genotypes and phenotypes of 162 families with a glomulin mutation.

A decade ago, we identified a novel gene, glomulin (GLMN) in which mutations cause glomuvenous malformations (GVMs). GVMs are bluish-purple cutaneous vascular lesions with characteristic glomus cells in the walls of distended venous channels. The discovery of the genetic basis for GVMs allowed the definition of clinical features to distinguish GVMs from other venous anomalies. The variation in phenotype was also highlighted: from a single punctate blue dot to a large plaque-like lesion. In this study, we screened GLMN in a large cohort of patients to broaden the spectrum of mutations, define their frequency and search for possible genotype-phenotype correlations. Taking into account 6 families published by others, a mutation in GLMN has been found in 162 families. This represents 40 different mutations; the most frequent one being present in almost 45% of them. Expressivity varies largely, without a genotype/phenotype relationship. Among 381 individuals with a mutation, we discovered 37 unaffected carriers, implying a penetrance of 90%. As nonpenetrant individuals may transmit the disease to their descendants, knowledge on the mutational status is needed for appropriate genetic counseling.

Germline Mutations in RASA1 Are Not Found in Patients with Klippel-Trenaunay Syndrome or Capillary Malformation with Limb Overgrowth.

The RASA1 gene encodes p120RASGAP, a multidomain cytoplasmic protein that acts as a negative regulator of the RAS signalling pathway. Heterozygous loss-of-function RASA1 mutations were identified in patients with Parkes Weber syndrome and multifocal capillary malformations. This syndrome is characterised by a capillary blush on an extremity, arteriovenous microfistulas, and bony and soft tissue hypertrophy. The aim of this study was to test RASA1 in 2 disorders characterised by asymmetric limb enlargement and vascular malformations, namely Klippel-Trenaunay syndrome and regional capillary malformation with overgrowth. We did not identify any clear pathogenic change in these patients. Thus, besides clinical and radiological criteria, RASA1 testing constitutes an additional tool to differentiate Parkes Weber syndrome of capillary malformation-arteriovenous malformation (CM-AVM) from overlapping disorders.

Variable Somatic TIE2 Mutations in Half of Sporadic Venous Malformations.

Venous malformations (VMs) are the most frequent vascular malformations referred to specialized vascular anomaly centers. A rare (1-2%) familial form, termed cutaneomucosal venous malformation (VMCM), is caused by gain-of-function mutations in TIE2. More recently, sporadic VMs, characterized by the presence of large unifocal lesions, were shown to be caused by somatic mutations in TIE2. These include a frequent L914F change, and a series of double mutations in cis. All of which cause ligand-independent receptor hyperphosphorylation in vitro. Here, we expanded our study to assess the range of mutations that cause sporadic VM. To test for somatic changes, we screened the entire coding region of TIE2 in cDNA from resected VMs by direct sequencing. We detected TIE2 mutations in 17/30 (56.7%) of the samples. In addition to previously detected mutations, we identified 7 novel somatic intracellular TIE2 mutations in sporadic VMs, including 3 that cause premature protein truncation.

Evaluation of Clinical Manifestations in Patients with Severe Lymphedema with and without CCBE1 Mutations.

The lymphedema-lymphangiectasia-intellectual disability (Hennekam) syndrome (HS) is characterised by a widespread congenital lymph vessel dysplasia manifesting as congenital lymphedema of the limbs and intestinal lymphangiectasia, accompanied by unusual facial morphology, variable intellectual disabilities and infrequently malformations. The syndrome is heterogeneous as mutations in the gene CCBE1 have been found responsible for the syndrome in only a subset of patients. We investigated whether it would be possible to predict the presence of a CCBE1 mutation based on phenotype by collecting clinical data of patients diagnosed with HS, with or without a CCBE1 mutation. We report here the results of 13 CCBE1 positive patients, 16 CCBE1 negative patients, who were clinically found to have classical HS, and 8 patients in whom the diagnosis was considered possible, but not certain, and in whom no CCBE1 mutation was identified. We found no statistically significant phenotypic differences between the 2 groups with the clinical HS phenotype, although the degree of lymphatic dysplasia tended to be more pronounced in the mutation positive group. We also screened 158 patients with less widespread and less pronounced forms of lymphatic dysplasia for CCBE1 mutations, and no mutation was detected in this group. Our results suggest that (1) CCBE1 mutations are present only in patients with a likely clinical diagnosis of HS, and not in patients with less marked forms of lymphatic dysplasia, and (2) that there are no major phenotypic differences between HS patients with or without CCBE1 mutations.

Prevalence and spectrum of SDHx mutations in pheochromocytoma and paraganglioma in patients from Belgium: an update.

Since the early 2000s, the prevalence and spectrum of mutations in genes encoding subunits of succinate dehydrogenase (SDHx) were reported in large cohorts of patients with pheochromocytoma (PC) and paraganglioma (PGL) from most Western countries. Unfortunately, in Belgium, no equivalent work was performed thus far. Therefore, the aim of the work was to look for mutations in SDHx genes and genotype-phenotype correlations in patients with PC and/or PGL from Belgium. Screening of the coding parts of SDHx genes and deletion search were performed in all patients with PC and/or PGL referred to the -Cliniques Universitaires Saint-Luc from 05/2003 to 05/2011. Genetic screening was performed in 59 unrelated head and neck (hn)PGLs (8 fami-lial) and 53 PCs (7 extra-adrenal; 3 metastatic). In hnPGLs, 10 different SDHD mutations (3 substitutions, 5 deletions, 2 splice site mutations) were detected in 16 patients, including 7 familial cases and 9 apparently sporadic cases. In the same subset, we found 8 different SDHB mutations (5 substitutions, 1 splice site mutation, 1 deletion, 1 duplication) in 10 patients with sporadic hnPGL without evidence of malignancy. No SDHx mutation was detected in patients harboring PCs and no SDHC mutation whatsoever. In conclusion, in our multicentric database of PC-PGLs from Belgium, (i) the prevalence of SDHx mutations was high in hnPGLs (44% in the whole subset, 37% of apparently sporadic cases); (ii) in sporadic cases, the prevalence of SDHB mutations was high (20%), similar to that of SDHD (18%); and (iii) no SDHx mutation was found in a subset of mostly adrenal, benign PCs.

IRF6 Screening of Syndromic and a priori Non-Syndromic Cleft Lip and Palate Patients: Identification of a New Type of Minor VWS Sign.

Van der Woude syndrome (VWS), caused by dominant IRF6 mutation, is the most common cleft syndrome. In 15% of the patients, lip pits are absent and the phenotype mimics isolated clefts. Therefore, we hypothesized that some of the families classified as having non-syndromic inherited cleft lip and palate could have an IRF6 mutation. We screened in total 170 patients with cleft lip with or without cleft palate (CL/P): 75 were syndromic and 95 were a priori part of multiplex non-syndromic families. A mutation was identified in 62.7 and 3.3% of the patients, respectively. In one of the 95 a priori non-syndromic families with an autosomal dominant inheritance (family B), new insights into the family history revealed the presence, at birth, of lower lip pits in two members and the diagnosis was revised as VWS. A novel lower lip sign was observed in one individual in this family. Interestingly, a similar lower lip sign was also observed in one individual from a 2nd family (family A). This consists of 2 nodules below the lower lip on the external side. In a 3rd multiplex family (family C), a de novo mutation was identified in an a priori non-syndromic CL/P patient. Re-examination after mutation screening revealed the presence of a tiny pit-looking lesion on the inner side of the lower lip leading to a revised diagnosis of VWS. On the basis of this data, we conclude that IRF6 should be screened when any doubt rises about the normality of the lower lip and also if a non-syndromic cleft lip patient (with or without cleft palate) has a family history suggestive of autosomal dominant inheritance.

Venous malformation: update on aetiopathogenesis, diagnosis and management.

The aim of this review was to discuss the current knowledge on aetiopathogenesis, diagnosis and therapeutic management of venous malformations (VMs). VMs are slow-flow vascular anomalies. They are simple, sporadic or familial (cutaneomucosal VMs or glomuvenous malformations), combined (e.g. capillaro-venous and capillaro-lymphaticovenous malformations) or syndromic (Klippel-Trenaunay, blue rubber bleb naevus and Maffucci). Genetic studies have identified causes of familial forms and of 40% of sporadic VMs. Another diagnostic advancement is the identification of elevated D-dimer level as the first biomarker of VMs within vascular anomalies. Those associated with pain are often responsive to low-molecular-weight heparin, which should also be used to avoid disseminated intravascular coagulopathy secondary to intervention, especially if fibrinogen level is low. Finally, development of a modified sclerosing agent, ethylcellulose-ethanol, has improved therapy. It is efficient and safe, and widens indications for sclerotherapy to sensitive and dangerous areas such as hands, feet and periocular area.

A novel association between RASA1 mutations and spinal arteriovenous anomalies.

BACKGROUND AND PURPOSE: CM-AVM is a recently recognized autosomal dominant disorder associated with mutations in RASA1. Arteriovenous lesions have been reported in the brain, limbs, and the face in 18.5% of patients. We report a novel association between RASA1 mutations and spinal arteriovenous anomalies. MATERIALS AND METHODS: In a collaborative study, 5 index patients (2 females, 3 males) with spinal AVMs or AVFs and cutaneous multifocal capillary lesions were investigated for the RASA1 gene mutation. RESULTS: All 5 patients were found to have RASA1 mutation (2 de novo, 3 familial), and all had multifocal capillary malformations at birth. Neurologic deficits developed at ages ranging from infancy to early adulthood. All spinal anomalies (2 AVMs at the conus, 1 AVM at the lumbosacral junction, and 1 cervical and 1 cervicothoracic AVF) were complex, extensive, and fast-flow lesions. All patients required treatment based on the clinical and/or radiologic appearance of the lesions. CONCLUSIONS: To our knowledge, an association of RASA1 mutation and spinal AVM/AVF has not been described. MR imaging screening of patients with characteristic CMs and neurologic symptoms presenting at a young age may be useful in detecting the presence of fast-flow intracranial or intraspinal arteriovenous anomalies before potentially significant neurologic insult has occurred.