Three children with Milroy disease and de novo mutations in VEGFR3

A novel stop-gain pathogenic variant in FLT4 and a nonsynonymous pathogenic variant in PTPN11 associated with congenital heart defects

BACKGROUND

Congenital heart defects (CHDs) are the most common congenital malformations, including structural malformations in the heart and great vessels. CHD complications such as low birth weight, prematurity, pregnancy termination, mortality, and morbidity depend on the type of defect.

METHODS

In the present research, genetic analyses via whole-exome sequencing (WES) was performed on 3 unrelated pedigrees with CHDs. The candidate variants were confirmed, segregated by PCR-based Sanger sequencing, and evaluated by bioinformatics analysis.

RESULTS

A novel stop-gain c.C244T:p.R82X variant in the FLT4 gene, as well as a nonsynonymous c.C1403T:p.T468M variant in the PTPN11 gene, was reported by WES. FLT4 encodes a receptor tyrosine kinase involved in lymphatic development and is known as vascular endothelial growth factor 3.

CONCLUSIONS

We are the first to report a novel c.C244T variant in the FLT4 gene associated with CHDs. Using WES, we also identified a nonsynonymous variant affecting protein-tyrosine phosphatase, the non-receptor type 11 (PTPN11) gene. The clinical implementation of WES can determine gene variants in diseases with high genetic and phenotypic heterogeneity like CHDs.

FLT4 Mutations Are Associated with Segmental Lymphatic Dysfunction and Initial Lymphatic Aplasia in Patients with Milroy Disease

This study explored mutations in the Fms-related tyrosine kinase 4/vascular endothelial growth factor receptor 3 gene (FLT4) and lymphatic defects in patients with Milroy disease (MD). Twenty-nine patients with lower limb lymphedema were enrolled. Sixteen patients had a familial history of MD, while 13 patients exhibited sporadic MD. Clinical signs, FLT4 mutations, indocyanine green (ICG) lymphography findings, and skin tissue immunohistochemical staining results were evaluated. Twenty-eight variants in FLT4 were identified. Twelve of these have previously been reported, while 16 are novel. Of the 28 variants, 26 are missense mutations, and the remaining two comprise a splicing mutation and a non-frame shift mutation. Twenty-five variants are located in the intracellular protein tyrosine kinase domain; three are located in the extracellular immunoglobulin domain. Substantially delayed contrast-enhanced tortuous lymphatic vessels were visualized to the ankle or knee level in 15 of 23 patients who underwent ICG lymphography. No initial lymphatic vessels were visualized in skin specimens from four patients who did not exhibit lymphatic vessels during imaging analyses. No specific variant was identified in relation to the unique clinical phenotype. Segmental dysfunction of lymphatic vessels and initial lymphatic aplasia are present in MD patients with FLT4 mutations.

[Primary congenital lymphedema: Milroy disease: the first case observed in the Department of Pediatrics at the University Hospital Yalgado Ouedraogo, Ouagadougou]

Congenital lymphedema is the accumulation of lymphatic fluid in the child's interstitial spaces. Milroy disease is a rare, hereditary, autosomal dominant condition showing incomplete penetrance. We report the case of a 7-year old little girl with Milroy disease examined for erysipelas on congenital big right leg. A family history of large congenital member existed. Physical examination showed big oedematous right leg painful to palpation, with skin lichenification and erysipelas. Paraclinical assessment objectified cutaneous lymphedema with vascular involvement suggestive of ectasia of the right saphenous vein. Female karyotype showed no abnormalities, despite the small chromosomal rearrangements. Treatment was based on physiotherapy, bandages, compression stockings and psychotherapy. This first case in Burkina Faso testifies to the rarity of the pathology but especially to the diagnostic difficulties related to the inadequacy of paraclinical investigations.

[Primary lymphedema in childhood]

Lymphedema results from impaired lymphatic transport with increased limb volume and is divided into primary and secondary forms. In children, primary lymphedema is the most frequent, with a sporadic, rarely familial form or associated with complex malformative or genetic disorders. Diagnosis of lymphedema is mainly clinical and lymphoscintigraphy is useful to assess the lymphatic function of both limbs precisely. The main differential diagnosis is overgrowth syndrome. Erysipelas (cellulitis) is the main complication, but psychological or functional discomfort may occur throughout the course of lymphedema. Lymphedema management is based on multilayer low-stretch bandage, skin care, and eventually manual lymph drainage. The objective of treatment is to reduce lymphedema volume and then stabilize it. Multilayer low-stretch bandage and elastic compression are the cornerstone of treatment. Parent's motivation, including self-management, is required to ensure the child's compliance and improve quality of life.

Genetics of lymphatic anomalies

Lymphatic anomalies include a variety of developmental and/or functional defects affecting the lymphatic vessels: sporadic and familial forms of primary lymphedema, secondary lymphedema, chylothorax and chylous ascites, lymphatic malformations, and overgrowth syndromes with a lymphatic component. Germline mutations have been identified in at least 20 genes that encode proteins acting around VEGFR-3 signaling but also downstream of other tyrosine kinase receptors. These mutations exert their effects via the RAS/MAPK and the PI3K/AKT pathways and explain more than a quarter of the incidence of primary lymphedema, mostly of inherited forms. More common forms may also result from multigenic effects or post-zygotic mutations. Most of the corresponding murine knockouts are homozygous lethal, while heterozygotes are healthy, which suggests differences in human and murine physiology and the influence of other factors.

Kampo Extract of Shinbuto Improved Refractory Diarrhea in Milroy's Disease

Milroy's disease is a hereditary congenital lymphedema caused by lymphatic obstruction. The legs are most commonly affected, but impaired intestinal lymphatic flow can cause loose bowel movements. Here, we report the use of the Kampo extract of shinbuto for successful treatment of and abdominal pain in a patient with Milroy's disease. Milroy's disease was diagnosed because of left leg lymph-edema with onset at birth. Conservative therapy with a compression bandage was applied. However, when the patient moved to Manila at 35 years of age, she was exposed to drastic temperature changes between the air-conditioned cold environment in her room and the hot and humid environment outside. She developed a constitutional state of coldness as in hiesho (冷え症). Then sudden lower abdominal pain and diarrhea began to occur 3 times per week and lasted at least 1 hour, sometimes accompanied by vomiting. It happened particularly when she was exposed to the cold environment and was not related to meals. Conventional anti-cholinergic or antidiarrhetic drugs had no therapeutic effect. These attacks continued in the same frequency for 3 years, so the patient visited a Kampo (traditional Japanese medicine) clinic, where her diagnosis of Milroy's disease–associated diarrhea and abdominal pain was augmented by the Kampo diagnosis of hiesho, suitai (body fluid retention). She was prescribed 7.5 g of shinbuto extract per day (TJ-30; Tsumura Co, Tokyo, Japan). The shinbuto extract significantly reduced abdominal pain and refractory diarrhea to about 2 days per month, and it tapered off completely in 3 months. Shinbuto is usually used against cold-induced diarrhea. Rewarming and water movement by shinbuto resulted in significant improvement in symptoms induced by hiesho and suitai triggered by the cold environment, though the patient's leg swelling did not change.

FLT4/VEGFR3 and Milroy disease: novel mutations, a review of published variants and database update

Milroy disease (MD) is an autosomal dominantly inherited primary lymphedema. In 1998, the gene locus for MD was mapped to 5q35.3 and variants in the VEGFR3 (FLT4) gene, encoding vascular endothelial growth factor receptor 3 (VEGFR3), were identified as being responsible for the majority of MD cases. Several reports have since been published detailing pathogenic FLT4 mutations. To date, a total of 58 different variants in FLT4, 20 of which are unpublished, have been observed in 95 families with MD. A review of published mutations is presented in this update. Furthermore, the unpublished variants are presented including clinical data. Comparison of clinical features in patients and their families with the same mutations reveals incomplete penetrance and variable expression, making genotype-phenotype correlations difficult. Most mutations are missense, but a few deletions and one splicing variant have also been reported. Several animal models have confirmed the role of VEGFR3 in lymphangiogenesis and studies show mutant VEGFR3 receptors are not phosphorylated. Here, an MD patient with the same p.Ile1053Phe change as seen in the Chy mouse is presented for the first time. This finding confirms that this mouse lineage is an excellent model for MD. All the data reviewed here has been submitted to a database based on the Leiden Open (source) Variation Database (LOVD) and is accessible online at www.lovd.nl/flt4.

Vascular anomalies: from genetics toward models for therapeutic trials

Vascular anomalies are localized abnormalities that occur during vascular development. Several causative genes have been identified not only for inherited but also for some sporadic forms, and the molecular pathways involved are becoming understood. This gives us the opportunity to generate animals carrying the causative genetic defects, which we hope model the phenotype seen in human patients. These models would enable us not only to test known antiangiogenic drugs, but also to develop novel approaches for treatment, directly targeting the mutated protein or molecules implicated in the pathophysiological signaling pathways.

Enteropathies of Infancy and Childhood

Intestinal biopsies constitute an ever-increasing portion of the pathologist's workload, accounting for nearly two-thirds of specimens accessioned yearly by the pathology department at The Children's Hospital of Philadelphia. The widespread use of endoscopy and gastrointestinal biopsies in current clinical practice presents the pathologist with a diversity of intestinal mucosal appearances corresponding to disease states of variable clinical severity, requiring close collaboration between clinician and pathologist for optimal interpretation. Many of the entities resulting in severe diarrhea of infancy have been recognized only in the last several decades, and although rare, the study of these disorders, especially when combined with the powerful methods of present-day genetics and molecular biology, has afforded important insights into enterocyte development and function, and intestinal immunity and tolerance. Other conditions once considered infrequent, such as celiac disease, have now been recognized to be much more common and can present with a wide range of pathologic features.

Sporadic in utero generalized edema caused by mutations in the lymphangiogenic genes VEGFR3 and FOXC2

OBJECTIVES

To investigate the genetic causes of idiopathic sporadic prenatal generalized edema.

STUDY DESIGN

In a series of 12 patients, in whom in utero generalized skin edema or hydrops fetalis had been diagnosed, we screened 3 lymphangiogenic genes, VEGFR3, FOXC2, and SOX18.

RESULTS

In 3 of the patients, we identified a mutation: 2 in VEGFR3 and 1 in FOXC2. Two of the mutations were de novo and one was either de novo or nonpenetrant inherited. In these patients, the generalized edema resorbed spontaneously, either in utero or after birth. In the 2 individuals with a VEGFR3 mutation, edema remained limited to lower limbs.

CONCLUSIONS

Mutations in the VEGFR3 and FOXC2 genes account for a subset of patients with unexplained in utero generalized subcutaneous edema and hydrops fetalis without family history of lymphedema. Lymphangiogenic genes should be screened for mutations in sporadic patients diagnosed with fetal edema.

From germline towards somatic mutations in the pathophysiology of vascular anomalies

The localized structural abnormalities that arise during vasculogenesis, angiogenesis and lymphangiogenesis, the developmental processes which give rise to the adult vasculature, are collectively termed vascular anomalies. The last 2 years have seen an explosion of studies that underscore paradominant inheritance, the combination of inherited changes with somatic second-hits to the same genes, as underlying rare familial forms. Moreover, local, somatic genetic defects that cause some of the common sporadic forms of these malformations have been unraveled. This highlights the importance of assessing for tissue-based genetic changes, especially acquired genetic changes, as possible pathophysiological causes, which have been largely overlooked except in the area of cancer research. Large-scale somatic screens will therefore be essential in uncovering the nature and prevalence of such changes, and their downstream effects. The identification of disease genes combined with exhaustive, precise clinical delineations of the entire spectra of associated phenotypes guides better management and genetic counseling. Such a synthesis of information on functional and phenotypic effects will enable us to make and use animal models to test less invasive, targeted, perhaps locally administered, biological therapies.

Primary mesenteric angiosarcoma in a child with associated lymphangiectasia: a case report

Angiosarcomas are rare tumors in children, usually occurring in soft tissue and liver. By contrast, angiosarcoma in adults usually occurs in the extremities in conjunction with lymphedema. Mesenteric angiosarcoma has only rarely been reported. When angiosarcomas arise in this location, they usually represent a 2nd malignancy following Hodgkin's lymphoma. We report a child who presented to the emergency room with an acute abdomen and underwent emergency surgery for a mesenteric angiosarcoma with associated lymphangiectasia of the bowel and mesentery. A brief review of the literature and the nomenclature of these unusual tumors are discussed.