De novo heterozygous missense variants in CELSR1 as cause of fetal pleural effusions and progressive fetal hydrops

Fetal hydrops as detected by prenatal ultrasound usually carries a poor prognosis depending on the underlying aetiology. We describe the prenatal and postnatal clinical course of two unrelated female probands in whom de novo heterozygous missense variants in the planar cell polarity gene CELSR1 were detected using exome sequencing. Using several in vitro assays, we show that the CELSR1 p.(Cys1318Tyr) variant disrupted the subcellular localisation, affected cell-cell junction, impaired planar cell polarity signalling and lowered proliferation rate. These observations suggest that deleterious rare CELSR1 variants could be a possible cause of fetal hydrops.

Evidence for common mechanisms of pathology between SHANK3 and other genes of Phelan-McDermid syndrome

Chromosome 22q13.3 deletion (Phelan-McDermid) syndrome (PMS, OMIM 606232) is a rare genetic condition that impacts neurodevelopment. PMS most commonly results from heterozygous contiguous gene deletions that include the SHANK3 gene or likely pathogenic variants of SHANK3 (PMS-SHANK3 related). Rarely, chromosomal rearrangements that spare SHANK3 share the same general phenotype (PMS-SHANK3 unrelated). Very recent human and model system studies of genes that likely contribute to the PMS phenotype point to overlap in gene functions associated with neurodevelopment, synaptic formation, stress/inflammation and regulation of gene expression. In this review of recent findings, we describe the functional overlaps between SHANK3 and six partner genes of 22q13.3 (PLXNB2, BRD1, CELSR1, PHF21B, SULT4A1, and TCF20), which suggest a model that explains the commonality between PMS-SHANK3 related and PMS-SHANK3 unrelated classes of PMS. These genes are likely not the only contributors to neurodevelopmental impairments in the region, but they are the best documented to date. The review provides evidence for the overlapping and likely synergistic contributions of these genes to the PMS phenotype.

Structure of the extracellular region of the adhesion GPCR CELSR1 reveals a compact module which regulates G protein-coupling

Cadherin EGF Laminin G seven-pass G-type receptors (CELSRs or ADGRCs) are conserved adhesion G protein-coupled receptors which are essential for animal development. CELSRs have extracellular regions (ECRs) containing 23 adhesion domains which couple adhesion to intracellular signaling. However, molecular-level insight into CELSR function is sparsely available. We report the 4.3 Å cryo-EM reconstruction of the mCELSR1 ECR with 13 domains resolved in the structure. These domains form a compact module mediated by interdomain interactions with contact between the N- and C-terminal domains. We show the mCELSR1 ECR forms an extended species in the presence of Ca 2+ , which we propose represents the antiparallel cadherin repeat dimer. Using assays for adhesion and G protein-coupling, we assign the N-terminal CADH1-8 module as necessary for cell adhesion and we show the C-terminal CAHD9-GAIN module regulates signaling. Our work provides important molecular context to the literature on CELSR function and opens the door towards further mechanistic studies.

Hybrid Lymphovenous Anastomosis Surgery Guided by Intraoperative Mesenteric Intranodal Lymphangiography for Refractory Nontraumatic Chylous Ascites: A Case Report

Refractory chylous ascites can cause significant nutritional and immunologic morbidity, but no clear treatment has been established. This article introduces a case of a 22-year-old female patient with an underlying lymphatic anomaly who presented with refractory chylous ascites after laparoscopic adnexectomy for ovarian teratoma which aggravated after thoracic duct embolization. Ascites (>3,000 mL/d) had to be drained via a percutaneous catheter to relieve abdominal distention and consequent dyspnea, leading to significant cachexia and weight loss. Two sessions of hybrid lymphovenous anastomosis (LVA) surgery with intraoperative mesenteric lymphangiography guidance were performed to decompress the lymphatics. The first LVA was done between inferior mesenteric vein and left para-aortic enlarged lymphatics in a side-to-side manner. The daily drainage of chylous ascites significantly decreased to 130 mL/day immediately following surgery but increased 6 days later. An additional LVA was performed between right ovarian vein and enlarged lymphatics in aortocaval area in side-to-side and end-to-side manner. The chylous ascites resolved subsequently without any complications, and the patient was discharged after 2 weeks. The patient regained weight without ascites recurrence after 22 months of follow-up. This case shares a successful experience of treating refractory chylous ascites with lymphatic anomaly through LVA, reversing the patient's life-threatening weight loss. LVA was applied with a multidisciplinary approach using intraoperative mesenteric lipiodol, and results showed the possibility of expanding its use to challenging problems in the intraperitoneal cavity.

Dysregulation of Lymphatic Endothelial VEGFR3 Signaling in Disease

Vascular endothelial growth factor (VEGF) receptor 3 (VEGFR3), a receptor tyrosine kinase encoded by the FLT4 gene, plays a significant role in the morphogenesis and maintenance of lymphatic vessels. Under both normal and pathologic conditions, VEGF-C and VEGF-D bind VEGFR3 on the surface of lymphatic endothelial cells (LECs) and induce lymphatic proliferation, migration, and survival by activating intracellular PI3K-Akt and MAPK-ERK signaling pathways. Impaired lymphatic function and VEGFR3 signaling has been linked with a myriad of commonly encountered clinical conditions. This review provides a brief overview of intracellular VEGFR3 signaling in LECs and explores examples of dysregulated VEGFR3 signaling in various disease states, including (1) lymphedema, (2) tumor growth and metastasis, (3) obesity and metabolic syndrome, (4) organ transplant rejection, and (5) autoimmune disorders. A more complete understanding of the molecular mechanisms underlying the lymphatic pathology of each disease will allow for the development of novel strategies to treat these chronic and often debilitating illnesses.

Ureteropelvic junction obstruction with primary lymphoedema associated with CELSR1 variants

BACKGROUND

Primary lymphoedema (PL) is a chronic, debilitating disease caused by developmental and functional defects of the lymphatic system. It is marked by an accumulation of interstitial fluid, fat and tissue fibrosis. There is no cure. More than 50 genes and genetic loci have been linked to PL. We sought to study systematically cell polarity signalling protein Cadherin Epidermal Growth Factor Laminin G Seven-pass G-type Receptor 1 (CELSR1) variants linked to PL.

METHODS

We investigated 742 index patients from our PL cohort using exome sequencing.

RESULTS

We identified nine variants predicted to cause CELSR1 loss of function. Four of them were tested for nonsense-mediated mRNA decay, but none was observed. Most of the truncated CELSR1 proteins would lack the transmembrane domain, if produced. The affected individuals had puberty/late-onset PL on lower extremities. The variants had a statistically significant difference in penetrance between female patients (87%) and male patients (20%). Eight variant carriers had a kidney anomaly, mostly in the form of ureteropelvic junction obstruction, which has not been associated with CELSR1 before. CELSR1 is located in the 22q13.3 deletion locus of the Phelan-McDermid syndrome. As variable renal defects are often seen in patients with the Phelan-McDermid syndrome, CELSR1 may be the long-sought gene for the renal defects.

CONCLUSION

PL associated with a renal anomaly suggests a CELSR1-related cause.

Lymphedema is associated with CELSR1 in Phelan-McDermid syndrome

Lymphedema is a troubling condition present in many disorders including the rare genetic disorder known as Phelan-McDermid syndrome (PMS). The neurobehavioral features of PMS, also known as 22q13.3 deletion syndrome, have been investigated, but little research exists on lymphedema in PMS. In this investigation, clinical and genetic data from 404 people with PMS were reviewed from the PMS-International Registry revealing a prevalence of 5% with lymphedema. Lymphedema was reported in 1 out of 47 people (2.1%) with PMS due to a SHANK3 variant and 19 out of 357 people (5.3%) with PMS due to 22q13.3 deletions. Lymphedema was more common among those in their teens or adulthood (p = 0.0011) and those with deletions >4 Mb. People with lymphedema had significantly larger deletions (mean 5.375 Mb) than those without lymphedema (mean 3.464 Mb, p = 0.00496). Association analysis identified a deletion of the CELSR1 gene to be the biggest risk factor (OR = 12.9 95% CI [2.9-56.2]). Detailed assessment of 5 subjects identified all had deletions of CELSR1, developed symptoms of lymphedema starting at age 8 or older, and typically responded well to standard therapy. In conclusion, this is the largest assessment of lymphedema in PMS to date and our results suggest that individuals with deletions >4 Mb or those with CELSR1 deletions should be assessed for lymphedema.

Genetic Profile of Arteriovenous Anomalies of the Head and Neck: Implications in Progression and Therapeutic Approaches

BACKGROUND

Arteriovenous Malformations (AVMs) are complex vascular anomalies that are usually sporadic and can have a variable clinical course. Treatment of AVMs can lead to severe sequeale and require thorough decision-making. There is a lack of standardized treatment protocols showing a growing need for pharmacological targeted therapies, specially in the most severe cases where surgery may not be feasible. Current knowledge in molecular pathways and genetic diagnosis have shed light in the pathophysiology of AVMs, opening possibilities for personalized treatment strategies.

METHODS

We performed a retrospective review of patients with head and neck AVMs treated in our department between 2003 and 2021 and performed a complete physical examination and imaging with ultrasound and angio-CT or MRI. Patients underwent genetic testing on AVMs' tissue samples and/or peripheral blood samples. Patients were grouped according to the genetic variant and a correlation between phenotype and genotype was studied.

RESULTS

22 patients with head and neck AVMs were included. We found eight patients with varians in MAP2K1, four patients with pathogenic variants in KRAS, six patients with pathogenic variants in RASA1, one patient with a pathogenic variant in BRAF, one patient with a pathogenic variant in NF1, another patient with a pathogenic variant in CELSR1 and one patient with pathogenic variants in PIK3CA and GNA14. Patients with MAP2K1 variants were the biggest group, with a moderate clinical course. Patients with KRAS mutations showed the most aggressive clinical course and a high rate of recurrence and osteolysis. Patients with RASA1 variants showed a characteristic phenotype with an ipsilateral capillary malformation in the neck.

CONCLUSION

We found a correlation between genotype and phenotype in this group of patients. The genetic diagnosis of AVMs is recommended in order to stablish a personalized treatment strategy. Targeted therapies are currently being investigated with promising results and may be recommended in addition to conventional surgical or embolization procedures, specially in the most complex cases.

LEVEL OF EVIDENCE

Level IV.

Updated consensus guidelines on the management of Phelan-McDermid syndrome

Phelan-McDermid syndrome (PMS) is a genetic condition caused by SHANK3 haploinsufficiency and characterized by a wide range of neurodevelopmental and systemic manifestations. The first practice parameters for assessment and monitoring in individuals with PMS were published in 2014; recently, knowledge about PMS has grown significantly based on data from longitudinal phenotyping studies and large-scale genotype-phenotype investigations. The objective of these updated clinical management guidelines was to: (1) reflect the latest in knowledge in PMS and (2) provide guidance for clinicians, researchers, and the general community. A taskforce was established with clinical experts in PMS and representatives from the parent community. Experts joined subgroups based on their areas of specialty, including genetics, neurology, neurodevelopment, gastroenterology, primary care, physiatry, nephrology, endocrinology, cardiology, gynecology, and dentistry. Taskforce members convened regularly between 2021 and 2022 and produced specialty-specific guidelines based on iterative feedback and discussion. Taskforce leaders then established consensus within their respective specialty group and harmonized the guidelines. The knowledge gained over the past decade allows for improved guidelines to assess and monitor individuals with PMS. Since there is limited evidence specific to PMS, intervention mostly follows general guidelines for treating individuals with developmental disorders. Significant evidence has been amassed to guide the management of comorbid neuropsychiatric conditions in PMS, albeit mainly from caregiver report and the experience of clinical experts. These updated consensus guidelines on the management of PMS represent an advance for the field and will improve care in the community. Several areas for future research are also highlighted and will contribute to subsequent updates with more refined and specific recommendations as new knowledge accumulates.

A Practical Approach to the Diagnosis of Lymphedema: A Narrative Review

INTRODUCTION

Lymphedema often presents as progressive, unremitting swelling and skin changes that are extremely distressing to patients. Hereditary lymphedema (HL) constitutes a type of primary lymphedema that is passed down through generations.

OBJECTIVES

The primary aims of this narrative review are to illustrate a framework to distinguish lymphedema from other causes of swelling and to differentiate the hereditary lymphedemas from each other.

RESULTS

A literature search was undertaken using relevant search terms. The articles were evaluated to generate a diagnostic algorithm to approach the swelling of an extremity using clinical and laboratory data. First, the stemmer sign should be evaluated. If it is negative, other causes should be considered. History and additional physical exam findings suggest either a primary or secondary cause of lymph-edema.

CONCLUSIONS

The hereditary lymphedemas have been classified by age of onset and then stratified by clinical criteria and genetic testing.

Investigation into the genetics of fetal congenital lymphatic anomalies

OBJECTIVE

Congenital lymphatic anomalies (LAs) arise due to defects in lymphatic development and often present in utero as pleural effusion, chylothorax, nuchal and soft tissue edema, ascites, or hydrops. Many LAs are caused by single nucleotide variants, which are not detected on routine prenatal testing.

METHODS

Demographic data were compared between two subcohorts, those with clinically significant fetal edema (CSFE) and isolated fetal edema. A targeted variant analysis of LA genes was performed using American College of Medical Genetics criteria on whole exome sequencing (WES) data generated for 71 fetal edema cases who remained undiagnosed after standard workup.

RESULTS

CSFE cases had poor outcomes, including preterm delivery, demise, and maternal preeclampsia. Pathogenic and likely pathogenic variants were identified in 7% (5/71) of cases, including variants in RASopathy genes, RASA1, SOS1, PTPN11, and a novel PIEZO1 variant. Variants of uncertain significance (VOUS) were identified in 45% (32/71) of cases. In CSFEs, VOUS were found in CELSR1, EPHB4, TIE1, PIEZO1, ITGA9, RASopathy genes, SOS1, SOS2, and RAF1.

CONCLUSIONS

WES identified pathogenic and likely pathogenic variants and VOUS in LA genes in 51% of fetal edema cases, supporting WES and expanded hydrops panels in cases of idiopathic fetal hydrops and fluid collections.

Imaging peripheral lymphatic dysfunction in chronic conditions

The lymphatics play important roles in chronic diseases/conditions that comprise the bulk of healthcare worldwide. Yet the ability to routinely image and diagnose lymphatic dysfunction, using commonly available clinical imaging modalities, has been lacking and as a result, the development of effective treatment strategies suffers. Nearly two decades ago, investigational near-infrared fluorescence lymphatic imaging and ICG lymphography were developed as routine diagnostic for clinically evaluating, quantifying, and treating lymphatic dysfunction in cancer-related and primary lymphedema, chronic venous disease, and more recently, autoimmune and neurodegenerative disorders. In this review, we provide an overview of what these non-invasive technologies have taught us about lymphatic (dys) function and anatomy in human studies and in corollary animal studies of human disease. We summarize by commenting on new impactful clinical frontiers in lymphatic science that remain to be facilitated by imaging.

Adhesion G protein-coupled receptors-Structure and functions

Adhesion G protein-coupled receptors (aGPCRs) are an ancient class of receptors that represent some of the largest transmembrane-integrated proteins in humans. First recognized as surface markers on immune cells, it took more than a decade to appreciate their 7-transmembrane structure, which is reminiscent of GPCRs. Roughly 30 years went by before the first functional proof of an interaction with a G protein was published. Besides classic features of GPCRs (extracellular N terminus, 7-transmembrane region, intracellular C terminus), aGPCRs display a distinct N-terminal structure, which harbors the highly conserved GPCR autoproteolysis-inducing (GAIN) domain with the GPCR proteolysis site (GPS) in addition to several functional domains. Several human diseases have been associated with variants of aGPCRs and subsequent animal models have been established to investigate these phenotypes. Much progress has been made in recent years to decipher the structure and functions of these receptors. This chapter gives an overview of our current understanding with respect to the molecular structural patterns governing aGPCR activation and the contribution of these giant molecules to the development of pathologies.

Dietary supplements in lymphedema

Lymphedema is a chronic inflammatory disorder resulting from ineffective fluid uptake by the lymphatic system, and the effects are principally felt in the lower limbs. The condition is said to be primary when caused by genetic mutations and secondary when caused by injuries, infections, or surgery. Lymphedema, a worldwide pathology, does not have an effective therapy so far. Leukotriene B4 has recently been identified as a key molecule in lymphedema pathogenesis. Surgical, nonsurgical, and pharmacological treatments have been proposed; however, they do not cure the disease and only ameliorate the symptoms. Nutrition and nutritional status are extremely important in lymphedema physiopathology. Obesity is a comorbidity that exacerbates the risk for secondary lymphedema and constitutes a negative prognostic factor. Indeed, anti-inflammatory foods and their effects on the inflammatory state and on oxidative stress are now being investigated for their possible therapeutic role in lymphedema. Although no special diet has so far been proven to be very effective, specific dietary tips could help in alleviating the edematous state of patients with lymphedema. A few supplements have been tested for lymphedema treatment. Among them, GARLIVE^® containing hydroxytyrosol, hesperidin, spermidine and vitamin A, exhibited promising effects in the animal model. Hydroxytyrosol, a polyphenol from olives, showed anti-inflammatory effects and reduced leukotriene B4 synthesis, thus holding promise as a potential natural candidate for lymphedema treatment.

CELSR1 variants are associated with partial epilepsy of childhood

CELSR1 gene, encoding cadherin EGF LAG seven-pass G-type receptor 1, is mainly expressed in neural stem cells during the embryonic period. It plays an important role in neurodevelopment. However, the relationship between CELSR1 and disease of the central nervous system has not been defined. In this study, we performed trios-based whole-exome sequencing in a cohort of 356 unrelated cases with partial epilepsy without acquired causes and identified CELSR1 variants in six unrelated cases. The variants included one de novo heterozygous nonsense variant, one de novo heterozygous missense variant, and four compound heterozygous missense variants that had one variant was located in the extracellular region and the other in the cytoplasm. The patients with biallelic variants presented severe epileptic phenotypes, whereas those with heterozygous variants were associated with a mild epileptic phenotype of benign epilepsy with centrotemporal spikes (BECTS). These variants had no or low allele frequency in the gnomAD database. The frequencies of the CELSR1 variants in this cohort were significantly higher than those in the control populations. The evidence from ClinGen Clinical-Validity Framework suggested a strong association between CELSR1 variants and epilepsy. These findings provide evidence that CELSR1 is potentially a candidate pathogenic gene of partial epilepsy of childhood.

Clinical staging and genetic profiling of Korean patients with primary lymphedema using targeted gene sequencing

Lymphedema is a progressive disease caused by lymphatic flow blockage in the lymphatic pathway. Primary (hereditary) lymphedema is caused by genetic mutations without secondary causes. We performed clinical profiling on Korean primary lymphedema patients based on their phenotypes using lymphoscintigraphy and made genetic diagnoses using a next-generation sequencing panel consisting of 60 genes known to be related to primary lymphedema and vascular anomalies. Of 27 patients included in this study, 14.8% of the patients had lymphedema of the upper extremities, 77.8% had lymphedema of the lower extremities and 7.4% had 4-limbs lymphedema. Based on the International Society of Lymphology staging, 14, 10, and 3 patients had stage 3, 2, and 1 lymphedema, respectively. Only one family was genetically confirmed to harbor likely pathogenic variants in CELSR1. The proband was carrying two likely pathogenic variants in CELSR1, while her symptomatic mother was confirmed to carry only one of the variants. Furthermore, two other variants of uncertain significance in CELSR1 were detected in other patients, making CELSR1 the most commonly altered gene in our study. The clinical and genetic profile of hereditary lymphedema reported here is the first such data series reported for South Korea.

Pediatric Lymphedema: Study of 180 Patients Referred to a Tertiary Lymphedema Clinic

BACKGROUND

Lymphedema is due to dysfunction of the lymphatic system. It can be primary or secondary. Pediatric lymphedema is more often primary and is a chronic disease with a heavy burden on quality of life.

METHODS

Medical records of patients under 18 years of age referred between 1996 and 2021 to the specialized lymphedema clinic at the Sainte-Justine University Hospital Center were reviewed. Demographic data, sex, age at presentation, location of the lymphedema, clinical features, genetic testing, symptoms, complications, investigations, and treatment were collected.

RESULTS

Of 180 referred patients, lymphedema was confirmed in 151, and 137 were primary lymphedema. Median age of apparition of primary lymphedema was 7.00 years and was significantly lower in boys than in girls. Primary congenital lymphedema was more frequent in boys (51.0%, 27.3% in girls, P = .007), and onset of primary lymphedema during adolescence was more frequent in girls (53.4%, 25.0% in boys, P = .001). Lower limbs were the most impacted (88.3%). Sixty patients had genetic testing, and 38 (63.3%) of them were discovered to have a pertinent genetic mutation. The most common mutated gene was the FLT4 gene (in 9 patients). Seven patients (5.1%) had associated extensive/central lymphatic malformation and 24 (17.6%) had a polymalformative syndrome/syndromic lymphedema.

CONCLUSIONS

Pediatric lymphedema is more frequent in girls, usually involves lower limb, and is most often sporadic, but often associated with a genetic mutation, and genetic testing should be performed.

Low Efficacy of Genetic Tests for the Diagnosis of Primary Lymphedema Prompts Novel Insights into the Underlying Molecular Pathways

Lymphedema is a chronic inflammatory disorder caused by ineffective fluid uptake by the lymphatic system, with effects mainly on the lower limbs. Lymphedema is either primary, when caused by genetic mutations, or secondary, when it follows injury, infection, or surgery. In this study, we aim to assess to what extent the current genetic tests detect genetic variants of lymphedema, and to identify the major molecular pathways that underlie this rather unknown disease. We recruited 147 individuals with a clinical diagnosis of primary lymphedema and used established genetic tests on their blood or saliva specimens. Only 11 of these were positive, while other probands were either negative (63) or inconclusive (73). The low efficacy of such tests calls for greater insight into the underlying mechanisms to increase accuracy. For this purpose, we built a molecular pathways diagram based on a literature analysis (OMIM, Kegg, PubMed, Scopus) of candidate and diagnostic genes. The PI3K/AKT and the RAS/MAPK pathways emerged as primary candidates responsible for lymphedema diagnosis, while the Rho/ROCK pathway appeared less critical. The results of this study suggest the most important pathways involved in the pathogenesis of lymphedema, and outline the most promising diagnostic and candidate genes to diagnose this disease.

Current Mechanistic Understandings of Lymphedema and Lipedema: Tales of Fluid, Fat, and Fibrosis

Lymphedema and lipedema are complex diseases. While the external presentation of swollen legs in lower-extremity lymphedema and lipedema appear similar, current mechanistic understandings of these diseases indicate unique aspects of their underlying pathophysiology. They share certain clinical features, such as fluid (edema), fat (adipose expansion), and fibrosis (extracellular matrix remodeling). Yet, these diverge on their time course and known molecular regulators of pathophysiology and genetics. This divergence likely indicates a unique route leading to interstitial fluid accumulation and subsequent inflammation in lymphedema versus lipedema. Identifying disease mechanisms that are causal and which are merely indicative of the condition is far more explored in lymphedema than in lipedema. In primary lymphedema, discoveries of genetic mutations link molecular markers to mechanisms of lymphatic disease. Much work remains in this area towards better risk assessment of secondary lymphedema and the hopeful discovery of validated genetic diagnostics for lipedema. The purpose of this review is to expose the distinct and shared (i) clinical criteria and symptomatology, (ii) molecular regulators and pathophysiology, and (iii) genetic markers of lymphedema and lipedema to help inform future research in this field.

Strong evidence for genotype-phenotype correlations in Phelan-McDermid syndrome: results from the developmental synaptopathies consortium

Individuals with Phelan-McDermid syndrome (PMS) present with a wide range of developmental, medical, cognitive and behavioral abnormalities. Previous literature has begun to elucidate genotype-phenotype associations that may contribute to the wide spectrum of features. Here, we report results of genotype-phenotype associations in a cohort of 170 individuals with PMS. Genotypes were defined as Class I deletions (including SHANK3 only or SHANK3 with ARSA and/or ACR and RABL2B), Class II deletions (all other deletions) or sequence variants. Phenotype data were derived prospectively from direct evaluation, caregiver interview and questionnaires, and medical history. Analyses revealed individuals with Class I deletions or sequence variants had fewer delayed developmental milestones and higher cognitive ability compared to those with Class II deletions but had more skill regressions. Individuals with Class II deletions were more likely to have a variety of medical features, including renal abnormalities, spine abnormalities, and ataxic gait. Those with Class I deletions or sequence variants were more likely to have psychiatric diagnoses including bipolar disorder, depression, and schizophrenia. Autism spectrum disorder diagnoses did not differ between groups. This study represents the largest and most rigorous genotype-phenotype analysis in PMS to date and provides important information for considering clinical functioning, trajectories and comorbidities as a function of specific genetic alteration.

CDH5, a Possible New Candidate Gene for Genetic Testing of Lymphedema

Background: Expressed by endothelial cells, CDH5 is a cadherin involved in vascular morphogenesis and in the maintenance of vascular integrity and lymphatic function. The main purpose of our study was to identify distinct variants of the CDH5 gene that could be associated with lymphatic malformations and predisposition for lymphedema. Methods and Results: We performed Next Generation Sequencing of the CDH5 gene in 235 Italian patients diagnosed with lymphedema but who tested negative for variants in known lymphedema genes. We detected six different variants in CDH5 five missense and one nonsense. We also tested available family members of the probands. For family members who carried the same variant as the proband, we performed lymphoscintigraphy to detect any lymphatic system abnormalities. Variants were modeled in silico. The results showed that CDH5 variants may contribute to the onset of lymphedema, although further in vitro studies are needed to confirm this hypothesis. Conclusions: Based on our findings, we propose CDH5 as a new gene that could be screened in patients with lymphedema to gather additional evidence.

EPHB4 mutation causes adult and adolescent-onset primary lymphedema

Primary lymphedema results from the anomalous development of the lymphatic system and typically presents during infancy, childhood, or adolescence. Adult-onset primary lymphedema is rare and mutations associated with this condition have not been identified. The purpose of this investigation was to search for variants that cause adult-onset primary lymphedema. We discovered an autosomal dominant EPHB4 mutation in a patient who developed unilateral leg lymphedema at age 39 years; the same mutation affected his son who presented with the disease at 14 years of age.

Lymphedema complicated by protein-losing enteropathy with a 22q13.3 deletion and the potential role of CELSR1: A case report

INTRODUCTION

22q13.3 deletion syndrome is a well-known syndrome characterized by typical clinical findings including neonatal hypotonia, absent or severely delayed speech, intellectual disability, and other various features, and detection of a heterozygous deletion of chromosome 22q13.3 with the involvement of at least part of SHANK3. It is reported that 10% to 29% of patients with 22q13.3 deletion syndrome present lymphedema. Protein-losing enteropathy (PLE) has never been reported in 22q13.3 deletion syndrome.

PATIENT CONCERNS

The patient presented to our institution for refractory hypoalbuminemia and chronic lymphedema in both legs.

DIAGNOSIS

The patient manifested intellectual disability, absent speech, tooth grinding, dysmorphic face, and abnormal hands and toenails. Copy-number variation sequencing confirmed the maternal deletion in 22q13.31-q13.33 (chr22:46285592-51244566, hg19). The patient was genetically diagnosed with 22q13.3 deletion syndrome.

INTERVENTIONS

Low-fat diets and medium-chain triglycerides supplements were prescribed. The patient was recommended to wear compression garments and elevate legs.

OUTCOMES

The symptom of diarrhea was resolved, but hypoalbuminemia persisted. Lower extremities lymphedema was gradually becoming severe.

CONCLUSIONS

Primary lymphedema and PLE can occur simultaneously in a patient with 22q13.3 deletion syndrome. The 2 phenotypes could share the same genetic etiology of congenital lymphatic abnormalities. CELSR1 deletion may play a role in lymphatic dysplasia. The case also provides additional proof of the pathogenic effect of CELSR1 on hereditary lymphedema.

Biology of Lymphedema

Simple Summary

Lymphedema is a chronic, debilitating disease of the lymphatic vasculature. Although several reviews focus on the anatomy and physiology of the lymphatic system, this review provides an overview of the lymphatic vasculature and, moreover, of lymphatic system dysfunction and lymphedema. Further, we aim at advancing the knowledge in the area of lymphatic system function and how dysfunction of the lymphatic system—as seen in lymphedema—affects physiological systems, such as the cardiovascular system, and how those might be modulated by lymphedema therapy.

Abstract

This narrative review portrays the lymphatic system, a poorly understood but important physiological system. While several reviews have been published that are related to the biology of the lymphatic system and lymphedema, the physiological alternations, which arise due to disturbances of this system, and during lymphedema therapy, are poorly understood and, consequently, not widely reported. We present an inclusive collection of evidence from the scientific literature reflecting important developments in lymphedema research over the last few decades. This review aims at advancing the knowledge on the area of lymphatic system function as well as how system dysfunction, as seen in lymphedema, affects physiological systems and how lymphedema therapy modulates these mechanisms. We propose that future studies should aim at investigating, in-detail, aspects that are related to fluid regulation, hemodynamic responses, and endothelial and/or vascular changes due to lymphedema and lymphedema therapy.

Segregation Analysis of Rare NRP1 and NRP2 Variants in Families with Lymphedema

Neuropilins are transmembrane coreceptors expressed by endothelial cells and neurons. NRP1 and NRP2 bind a variety of ligands, by which they trigger cell signaling, and are important in the development of lymphatic valves and lymphatic capillaries, respectively. This study focuses on identifying rare variants in the NRP1 and NRP2 genes that could be linked to the development of lymphatic malformations in patients diagnosed with lymphedema. Two hundred and thirty-five Italian lymphedema patients, who tested negative for variants in known lymphedema genes, were screened for variants in NRP1 and NRP2. Two probands carried variants in NRP1 and four in NRP2. The variants of both genes segregated with lymphedema in familial cases. Although further functional and biochemical studies are needed to clarify their involvement with lymphedema and to associate NRP1 and NRP2 with lymphedema, we suggest that it is worthwhile also screening lymphedema patients for these two new candidate genes.

TIE1 as a Candidate Gene for Lymphatic Malformations with or without Lymphedema

TIE1 is a cell surface protein expressed in endothelial cells. Involved in angiogenesis and lymphangiogenesis, including morphogenesis of lymphatic valves, TIE1 is important for lymphatic system functional integrity. The main purpose of this study was to identify different variants in the TIE1 gene that could be associated with lymphatic malformations or dysfunction and predisposition for lymphedema. In a cohort of 235 Italian lymphedema patients, who tested negative for variants in known lymphedema genes, we performed a further test for new candidate genes, including TIE1. Three probands carried different variants in TIE1. Two of these segregated with lymphedema or lymphatic dysfunction in familial cases. Variants in TIE1 could contribute to the onset of lymphedema. On the basis of our findings, we propose TIE1 as a candidate gene for comprehensive genetic testing of lymphedema.