Capillary malformation-arteriovenous malformation, a new clinical and genetic disorder caused by RASA1 mutations

Noonan, Costello and cardio–facio–cutaneous syndromes: dysregulation of the Ras–MAPK pathway

A class of developmental disorders caused by dysregulation of the Ras-induced mitogen-activated protein kinase (MAPK) cascade (the Ras–MAPK pathway) has emerged. Three of these disorders – Noonan, Costello and cardio–facio–cutaneous syndromes – have overlapping phenotypic features characterised by distinctive facial dysmorphia, cardiac defects, musculoskeletal and cutaneous abnormalities, and neurocognitive delay. The germline mutations associated with these disorders are in genes that encode proteins of the Ras–MAPK pathway. In vitro studies have determined that the overwhelming majority of these mutations result in increased signal transduction down the pathway, but usually to a lesser degree than somatic mutations in the same genes that are associated with cancer. The Ras–MAPK pathway is essential in the regulation of the cell cycle, differentiation, growth and senescence, so it is not surprising that germline mutations that affect its function have profound effects on development. Here we review the clinical consequences of the known molecular lesions associated with Noonan syndrome, Costello syndrome and cardio–facio–cutaneous syndrome, and explore possible therapeutic modalities for treatment.

p120-Ras GTPase activating protein (RasGAP): a multi-interacting protein in downstream signaling

p120-RasGAP (Ras GTPase activating protein) plays a key role in the regulation of Ras-GTP bound by promoting GTP hydrolysis via its C-terminal catalytic domain. The p120-RasGAP N-terminal part contains two SH2, SH3, PH (pleckstrin homology) and CaLB/C2 (calcium-dependent phospholipid-binding domain) domains. These protein domains allow various functions, such as anti-/pro-apoptosis, proliferation and also cell migration depending of their distinct partners. The p120-RasGAP domain participates in protein-protein interactions with Akt, Aurora or RhoGAP to regulate functions described bellow. Here, we summarize, in angiogenesis and cancer, the various functional roles played by p120-RasGAP domains and their effector partners in downstream signaling.

Parkes Weber syndrome, vein of Galen aneurysmal malformation, and other fast-flow vascular anomalies are caused by RASA1 mutations

Capillary malformation-arteriovenous malformation (CM-AVM) is a newly recognized autosomal dominant disorder, caused by mutations in the RASA1 gene in six families. Here we report 42 novel RASA1 mutations and the associated phenotype in 44 families. The penetrance and de novo occurrence were high. All affected individuals presented multifocal capillary malformations (CMs), which represent the hallmark of the disorder. Importantly, one-third had fast-flow vascular lesions. Among them, we observed severe intracranial AVMs, including vein of Galen aneurysmal malformation, which were symptomatic at birth or during infancy, extracranial AVM of the face and extremities, and Parkes Weber syndrome (PKWS), previously considered sporadic and nongenetic. These fast-flow lesions can be differed from the other two genetic AVMs seen in hereditary hemorrhagic telangiectasia (HHT) and in phosphatase and tensin homolog (PTEN) hamartomatous tumor syndrome. Finally, some CM-AVM patients had neural tumors reminiscent of neurofibromatosis type 1 or 2. This is the first extensive study on the phenotypes associated with RASA1 mutations, and unravels their wide heterogeneity.

Generation of mice with a conditional allele of the p120 Ras GTPase-activating protein

p120 Ras GTPase-activating protein (RasGAP) encoded by the rasa1 gene in mice is a prototypical member of the RasGAP family of proteins involved in negative-regulation of the p21 Ras proto-oncogene. RasGAP has been implicated in signal transduction through a number of cell surface receptors. In humans, inactivating mutations in the coding region of the RASA1 gene cause capillary malformation arteriovenous malformation. In mice, generalized disruption of the rasa1 gene results in early embryonic lethality associated with defective vasculogenesis and increased apoptosis of neuronal cells. The early lethality in this mouse model precludes its use to further study the importance of RasGAP as a regulator of cell function. Therefore, to circumvent this problem, we have generated a conditional rasa1 knockout mouse. In this mouse, an exon that encodes a part of the RasGAP protein essential for catalytic activity has been flanked by loxP recognition sites. With the use of different constitutive and inducible Cre transgenic mouse lines, we show that deletion of this exon from the rasa1 locus results in effective loss of expression of catalytically-active RasGAP from a variety of adult tissues. The conditional rasa1 mouse will be useful for the analysis of the role of RasGAP in mature cell types.

Physiology, pathology and relatedness of human tissues from gene expression meta-analysis

BACKGROUND

Development and maintenance of the identity of tissues is of central importance for multicellular organisms. Based on gene expression profiles, it is possible to divide genes in housekeeping genes and those whose expression is preferential in one or a few tissues and which provide specialized functions that have a strong effect on the physiology of the whole organism.

RESULTS

We have surveyed the gene expression in 78 normal human tissues integrating publicly available microarray gene expression data. A total amount of 1601 genes were identified as selectively expressed in one or more tissues. The tissue-selective genes covered a wide range of cellular and molecular functions, and could be linked to 361 human diseases with Mendelian inheritance. Based on the gene expression profiles, we were able to form a network of tissues reflecting their functional relatedness and, to certain extent, their development. Using co-citation driven gene network technique and promoter analysis, we predicted a transcriptional module where the co-operation of the transcription factors E2F and NF-kappaB can possibly regulate a number of genes involved in the neurogenesis that takes place in the adult hippocampus.

CONCLUSIONS

Here we propose that integration of gene expression data from Affymetrix GeneChip experiments is possible through re-annotation and commonly used pre-processing methods. We suggest that some functional aspects of the tissues can be explained by the co-operation of multiple transcription factors that regulate the expression of selected groups of genes.

Prediction of human disease genes by human-mouse conserved coexpression analysis

BACKGROUND

Even in the post-genomic era, the identification of candidate genes within loci associated with human genetic diseases is a very demanding task, because the critical region may typically contain hundreds of positional candidates. Since genes implicated in similar phenotypes tend to share very similar expression profiles, high throughput gene expression data may represent a very important resource to identify the best candidates for sequencing. However, so far, gene coexpression has not been used very successfully to prioritize positional candidates.

METHODOLOGY/PRINCIPAL FINDINGS

We show that it is possible to reliably identify disease-relevant relationships among genes from massive microarray datasets by concentrating only on genes sharing similar expression profiles in both human and mouse. Moreover, we show systematically that the integration of human-mouse conserved coexpression with a phenotype similarity map allows the efficient identification of disease genes in large genomic regions. Finally, using this approach on 850 OMIM loci characterized by an unknown molecular basis, we propose high-probability candidates for 81 genetic diseases.

CONCLUSION

Our results demonstrate that conserved coexpression, even at the human-mouse phylogenetic distance, represents a very strong criterion to predict disease-relevant relationships among human genes.

RASA1 mutations may cause hereditary capillary malformations without arteriovenous malformations

BACKGROUND

Capillary malformation (CM), a common vascular abnormality, is often present among family members. Recently a rare form of hereditary vascular malformation termed capillary malformation-arteriovenous malformation (CM-AVM) was shown to be caused by heterozygous mutations in RASA1, encoding RAS p21 protein activator 1. CM-AVM is characterized by multiple, small CMs associated with either AVM or arteriovenous fistula (AVF) in affected individuals or at least one of their family members.

OBJECTIVES

The purpose of the study was to find out whether CMs in the absence of AVM/AVF are associated with RASA1 mutations.

PATIENTS/METHODS

We assessed three families comprising 14 affected individuals with CMs. Linkage to the RASA1 locus was evaluated using microsatellite markers. The RASA1 gene was scrutinized for pathogenic mutations using denaturing high-performance liquid chromatography screening and direct sequencing.

RESULTS

AVM/AVF was identified in one of three affected families. CM without AVM/AVF was found to map in one large kindred to the RASA1 locus. Direct sequencing revealed novel heterozygous mutations segregating with CM in all three families. The mutations are predicted to result in premature termination of translation and RASA1 haplo-insufficiency.

CONCLUSIONS

We have demonstrated that the spectrum of clinical manifestations due to mutations in RASA1 is wider than previously thought and also includes typical CMs not associated with AVM/AVF.

Intramedullary spinal arteriovenous malformation in a boy of familial cerebral cavernous hemangioma

OBJECT

The coexistence of spinal arteriovenous malformation (AVM) and a familial cerebral cavernous hemangioma (CCH) is extremely rare.

METHODS

A 9-year-old boy suddenly developed severe paraplegia and urinary dysfunction. Spinal magnetic resonance imaging (MRI) scan revealed a cervical and upper thoracic intramedullary lesion. Due to acute neurological dysfunction, the patient underwent emergency surgical exploration. An intramedullary vascular lesion was found and excised. Pathologically, AVM was noted. After the surgery, the boy was ambulatory with left lower limb stiffness. MRI scan of the brain revealed multiple cerebral cavernous hemangioma. Symptomatic multiple CCH in his mother and grandmother were also noted.

CONCLUSIONS

We concluded that the presence of spinal AVM should be suspected if the patient with familial CCH develops the signs of space-occupying lesion of the spinal cord, facilitating early diagnosis of the spinal AVM.

Evidence for clinical and genetic heterogeneity in hereditary benign telangiectasia

BACKGROUND

Telangiectases are abnormal dilatations of end vessels in the subpapillary plexus of the papillary dermis. Hereditary benign telangiectasia (HBT) (OMIM 187260) is a genetic skin disorder, characterized by multiple cutaneous telangiectases appearing in the first years of life in various locations. Several familial cases of HBT have been described displaying autosomal dominant inheritance. In some of the described pedigrees, telangiectases are limited to sun-exposed areas, whereas in others lesions are randomly distributed over the body. The disorder has been previously mapped to a 7Mb interval on chromosome 5q14 (CMC1 locus) in an Italian pedigree with randomly distributed telangiectases.

OBJECTIVES

A large pedigree of HBT with photodistributed lesions is described. We sought to determine whether photodistributed HBT is linked to the CMC1 locus.

METHODS

In all, 35 family members were examined. DNA was extracted from blood and saliva samples. Linkage analysis to CMC1 locus on chromosome 5q14 was screened by using 3 polymorphic markers.

RESULTS

In all, 23 family members were found to have variable numbers of cutaneous radiating macular telangiectases, measuring 1 to 3 cm and distributed over the face, back of the hands, and forearms. HBT in this family is inherited in an autosomal dominant pattern with incomplete penetrance. Linkage to the CMC1 locus was excluded.

LIMITATION

Only one family, although very large, was studied in this project.

CONCLUSIONS

Clinical and genetic heterogeneity is evident in HBT. Photodistributed HBT is not related pathogenically to capillary malformations or to randomly distributed hereditary telangiectases and should be recognized as a separate entity.

What's new in the neuro-cardio-facial-cutaneous syndromes?

The RAS-MAPKinase pathway is a signal transduction cascade which has been studied extensively during the last decades for its role in human oncogenesis. Activation of this cascade is controlled by cycling of the RAS protein between an inactive and an active state and by phosphorylation of downstream proteins. The signalling cascade regulates cell proliferation, differentiation and survival. Disturbed RAS signalling in malignancies is caused by acquired somatic mutations in RAS genes or other components of this pathway. Recently, germline mutations in genes coding for different components of the RAS signalling cascade have been recognized as the cause of several phenotypically overlapping disorders, recently referred to as the neuro-cardio-facial-cutaneous syndromes. Neurofibromatosis type 1, Noonan, LEOPARD, Costello and cardiofaciocutaneous syndromes all present with variable degrees of psychomotor delay, congenital heart defects, facial dysmorphism, short stature, skin abnormalities and a predisposition for malignancy. These findings point to important roles for this evolutionary conserved pathway in oncogenesis, development, cognition and growth.

CONCLUSION

it has become obvious in recent years that the neuro-cardio-facial-cutaneous syndromes all share a common genetic and pathophysiologic basis. Dysregulation of the RAS-MAPKinase pathway is caused by germline mutations in genes involved in this pathway. Undoubtedly more genes causing related syndromes will be discovered in the near future since there are still a substantial number of genes in the pathway that are not yet associated with a known syndrome.

Pulmonary vascular manifestations of hereditary hemorrhagic telangiectasia (rendu-osler disease)

Hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler-Weber disease is a genetic disorder with autosomal dominance and variable penetrance, characterized by epistaxis, telangiectasia and visceral manifestations of the disease. The estimated minimal prevalence is 1/10,000 inhabitants. The diagnosis is established on clinical criteria, and may be further confirmed by the identification of causative mutations in either the ENG or the ACVRL1 gene coding for endoglin and ALK1, respectively. Pulmonary vascular manifestations of HHT include pulmonary arteriovenous malformations (PAVMs; especially in patients with ENG mutations) and less frequently pulmonary hypertension (especially in patients with ACVRL1 mutations). In 15-33% of patients with HHT, PAVMs consist of abnormal communications between pulmonary arteries and pulmonary veins, causing right-to-left shunting, and thus, frequently hypoxemia and dyspnea on exertion, although PAVMs may remain asymptomatic and frequently undiagnosed unless complications occur. PAVMs result in severe and frequent complications often at a young age, which may reveal the diagnosis, e.g. transient ischemic attack and cerebral stroke (10-19% of patients), systemic severe infections and abscesses (including cerebral abscess in 5-19% of patients), and rarely massive hemoptysis or hemothorax. Infections in HHT are related to the right-to-left shunting that bypasses the pulmonary capillaries and facilitates the passage of septic or aseptic emboli into the systemic and especially cerebral circulation, and potentially to minor defects in innate immunity. Treatment of PAVMs based on transcatheter coil vaso-occlusion of the feeding artery significantly decreases right-to-left shunting, hypoxemia and dyspnea on exertion, and reduces the risk of systemic complications. Long-term follow-up is warranted after transcatheter vaso-occlusion of PAVMs due to frequent recanalization of treated PAVMs and development or growth of untreated PAVMs. Patients with HHT should be informed of the risk of PAVM and potentially severe complications occurring in heretofore asymptomatic subjects. All adult patients with HHT should be proposed systematic screening for PAVM, by contrast echocardiography (preceded by anteroposterior chest radiograph) or computed tomography of the chest. Pulmonary hypertension is rare in HHT, and may be due either to systemic arteriovenous shunting in the liver increasing cardiac output or be clinically and histologically indistinguishable from idiopathic pulmonary arterial hypertension. Pulmonary hypertension is detected by systematic examination of right cardiac cavities and tricuspid regurgitation flow at echocardiography, and the diagnosis is established by right heart catheterization.

The phakomatoses: dermatologic clues to neurologic anomalies

The phakomatoses of particular interest to neurologists including Sturge-Weber syndrome, neurofibromatosis type 1, neurofibromatosis type 2, Bannayan-Riley-Ruvalcaba syndrome, and Proteus syndrome are presented. The physical manifestations required for clinical diagnosis, the neurologic features, and recommendations for management are given. The molecular etiology and genetic aspects of these disorders are briefly discussed as well as future implications of on-going research.

Parkes Weber syndrome occurring in a family with capillary malformations

Parkes Weber syndrome is a disorder characterized by cutaneous blush, arteriovenous fistula, and overgrowth of the affected limb. It has been differentiated from Klippel-Trenaunay syndrome on the basis of the presence of arteriovenous fistula that are always absent in the latter. We report a case of Parkes Weber syndrome with diffuse arteriovenous high flow leading to hemodynamic complications but without radiographic evidence of arteriovenous fistula. There are multiple individuals in the family with capillary malformations inherited in an autosomal dominant pattern. These observations reinforce the suggestions that Parkes Weber syndrome and capillary malformations may share a common pathogenetic pathway.

Beware of varicose veins in a patient with sturge-weber syndrome

This report describes the case of a 21-year-old man with a history of Sturge-Weber syndrome and varicose veins. Examination of the left lower limb revealed the presence of significant port-wine staining, and hypertrophy. Duplex examination revealed a severely hypoplastic deep venous system with a tortuous, dilated, long saphenous vein, which was competent and responsible for a significant proportion of venous return from the left lower limb, thus confirming the diagnosis of Klippel-Trenaunay syndrome. The patient was counseled regarding the implications of the diagnosis and was treated conservatively. The association between these two rare syndromes has been previously reported in the nonvascular literature. We believe that features of the Sturge-Weber syndrome or other forms of mesodermal phakomatosis should alert a clinician to the presence of lower limb venous malformations, which will need to be investigated prior to embarking on what could be potentially detrimental venous surgery.

Current Endovascular Management of Maxillofacial Vascular Malformations

Maxillofacial vascular malformations (MFVMs) are formed due to an error of vascular morphogenesis. They generally grow in proportion to the growth of the affected child but may increase in size secondary to various triggering factors such as increased blood flow, arterial occlusion, and venous thrombosis. The development of an individual lesion, especially if it is high flow, may be stimulated by various factors. High flow in an existing MFVM can induce arteriovenous shunting, which, in turn, increases flow demand, cascading enlargement of the malformation. Increased understanding of these additional physiologic variants may help to define their clinical presentation and evolution and assist in designing therapeutic strategies.

Disruption of diacylglycerol kinase delta (DGKD) associated with seizures in humans and mice

We report a female patient with a de novo balanced translocation, 46,X,t(X;2)(p11.2;q37)dn, who exhibits seizures, capillary abnormality, developmental delay, infantile hypotonia, and obesity. The 2q37 breakpoint observed in association with the seizure phenotype is of particular interest, because it lies near loci implicated in epilepsy in humans and mice. Fluorescence in situ hybridization mapping of the translocation breakpoints showed that no known genes are disrupted at Xp11.2, whereas diacylglycerol kinase delta (DGKD) is disrupted at 2q37. Expression studies in Drosophila and mouse suggest that DGKD is involved in central nervous system development and function. Electroencephalographic assessment of Dgkd mutant mice revealed abnormal epileptic discharges and electrographic seizures in three of six homozygotes. These findings implicate DGKD disruption by the t(X;2)(p11.2;q37)dn in the observed phenotype and support a more general role for DGKD in the etiology of seizures.

Vascular malformations. Part II: associated syndromes

Cutaneous vascular malformations are rare disorders representing errors in vascular development. These lesions occur much less commonly but are often confused with the common infantile hemangioma. It is important to properly diagnose vascular malformations because of their distinct differences in morbidity, prognosis and treatment. Vascular malformations may be associated with underlying disease or systemic anomalies. Several of these syndromes are well defined and can often be distinguished on the basis of the flow characteristics of the associated vascular malformation.

LEARNING OBJECTIVE

At the completion of this learning activity, participants should be able to better recognize underlying diseases or systemic anomalies that may be associated with vascular malformations. Participants should also better understand the various syndromes and conditions discussed and become more familiar with their management.

Vascular malformations: Part I

Cutaneous vascular malformations are rare disorders representing errors in vascular development. These lesions occur much less commonly but are often confused with the common infantile hemangioma. It is important to properly diagnose vascular malformations because of their distinct differences in morbidity, prognosis and treatment. Vascular malformations may be associated with underlying disease or systemic anomalies. Several of these syndromes are well defined and can often be distinguished on the basis of the flow characteristics of the associated vascular malformation.

LEARNING OBJECTIVE

At the completion of this learning activity, participants should have a better understanding of the different types of cutaneous vascular malformations. Because of the importance of proper diagnosis of these lesions, participants should also be better able to direct correct management and treatment.

New techniques for the evaluation and therapeutic planning of patients with Klippel-Trénaunay syndrome

BACKGROUND

Klippel-Trénaunay syndrome (KTS) is a well-known eponym for a capillary-lymphatic-venous malformation which is associated with soft tissue and skeletal hypertrophy, usually of one or more limbs. Plain films, sonograms, conventional venograms, and arteriograms have been employed for the evaluation of the disease.

OBJECTIVE

To demonstrate the usefulness of multidetector computed tomography (MDCT) and fast 3-dimensional magnetic resonance imaging (3D-MR) venography for the assessment and therapeutic planning of patients with KTS.

METHODS

A prospective study in 16 consecutive patients with KTS using MDCT and 3D-MR venography, performed between January 2004 and January 2006 in a university hospital in Pamplona, Spain.

RESULTS

In nearly all patients, persistent embryologic veins were observed, and in one subject aplasia/atresia of the whole deep venous system of the affected extremity was seen. In four individuals hypoplasia of the femoral vein was observed; one subject had duplication of the femoral vein, and in three patients aplasia/atresia of this vein was found. Only half of the patients had normal popliteal veins. In one patient, aneurysmal dilatation of the popliteal vein was detected, and in six subjects, aplasia of this vein was observed. The presence of geographic stains was suggestive of hypoplasia and/or aplasia of femoral and popliteal veins.

LIMITATIONS

The small size of the group of patients with KTS, which is related to low incidence of the disease.

CONCLUSIONS

MDCT and 3D-MR venography are extremely helpful for the global evaluation of patients with KTS. Information regarding soft tissue and bony anatomy as well as information about superficial and deep venous systems may be obtained with a single exam.

A fourth locus for hereditary hemorrhagic telangiectasia maps to chromosome 7

Hereditary hemorrhagic telangiectasia (HHT) is a genetically and clinically heterogeneous multisystem vascular dysplasia. Mutations of the endoglin and ACVRL1 genes are known to cause HHT. However, existence of HHT families in which linkage to these genes has been excluded has suggested that other gene(s) can cause HHT in some families. Recently, a family was reported to be linked to chromosome 5q, the HHT3 locus. Here we report on linkage results on a family with classic features of HHT, albeit a less severe phenotype with regards to epistaxis and telangiectases, in which linkage to HHT1, HHT2, and HHT3 is ruled out. Whole genome linkage analysis and fine mapping results suggested a 7 Mb region on the short arm of chromosome 7 (7p14) between STR markers D7S2252 and D7S510. We obtained a maximum two point LOD score of 3.60 with the STR marker D7S817. This region was further confirmed by haplotype analysis. These findings suggest the presence of another gene causing HHT (HHT4). The features in this family that strongly suggest the presence of a hereditary, multisystem vascular dysplasia would be easily missed during the typical evaluation and management of a patient with an AVM. This family helps emphasize the need to obtain a very detailed, targeted medical and family history for even mild, infrequent but recurring nosebleed, subtle telangiectases. Further studies of the candidate region and the identification of the gene responsible for the vascular anomalies in this family will add to our understanding of vascular morphogenesis and related disorders.

[Pathogenesis and genetics of vascular anomalies]

Vascular anomalies, divided into vascular tumors and vascular malformations, are localized defects of angiogenesis. Hemangiomas appear soon after birth, grow quickly, and then spontaneously, but slowly, disappear. In contrast, vascular malformations are congenital defects of vascular development that grow proportionately with the child. Most vascular anomalies are considered non-hereditary. However, due to detailed analysis inherited forms have been observed, which has led to identify mutations in three genes causing familial vascular malformations: in the angiopoietin receptor TIE2 in mucocutaneous venous malformations (VMCM), in glomulin in glomuvenous malformations (GVM) and in RASA1 in the newly recognized phenotype capillary malformation-arteriovenous malformation (CM-AVM). Identification of the causative genes has permitted more precise diagnosis and differential diagnosis, evaluation of phenotypic variability among patients with a proven mutation, study of used treatments in more homogeneous patient groups, and elucidation of the etiopathogenic mechanisms behind vascular malformations. Further studies are needed to unravel the role of genetic variations in the various vascular malformations and to unravel the precise molecular mechanisms that lead to development of these vascular lesions. This should provide development of new-targeted therapies.

The human and mouse complement of SH2 domain proteins-establishing the boundaries of phosphotyrosine signaling

SH2 domains are interaction modules uniquely dedicated to the recognition of phosphotyrosine sites and are embedded in proteins that couple protein-tyrosine kinases to intracellular signaling pathways. Here, we report a comprehensive bioinformatics, structural, and functional view of the human and mouse complement of SH2 domain proteins. This information delimits the set of SH2-containing effectors available for PTK signaling and will facilitate the systems-level analysis of pTyr-dependent protein-protein interactions and PTK-mediated signal transduction. The domain-based architecture of SH2-containing proteins is of more general relevance for understanding the large family of protein interaction domains and the modular organization of the majority of human proteins.

Klippel-Trenaunay-Weber syndrome and intramedullary cervical cavernoma: a very rare association. Case report

BACKGROUND

Klippel-Trenaunay-Weber syndrome is a rare mesodermal phakomatosis characterized by cutaneous hemangiomata, venous varicosities, and osseous-soft tissue hypertrophy of the affected limb. As the pathologic aspect of KTWS arises from the site in which malformations occur, the clinical picture varies widely from patients who complain for cosmetic reasons to patients with life-threatening lesions.

CASE DESCRIPTION

We describe a very rare case in which KTWS was associated with a cervical intramedullary cavernous angioma surgically treated.

CONCLUSION

This report confirms the wide range of expression of vascular abnormalities in neurocutaneous developmental diseases and the need of a careful multisystemic evaluation of these patients.

Syndrome de Parkes-Weber familial

INTRODUCTION

Parkes-Weber syndrome is usually described as a sporadic form of osteohypertrophic angiodysplasia. However, family forms of Klippel-Trenaunay syndrome have been described. We report the first familial case of Parkes-Weber syndrome.

OBSERVATION

A boy born at 27 weeks and 6 days of amenorrhea with extensive plane angioma of the right lower limb, right lower part of the back and abdomen. We also noted hypertrophy of this member with venous dilatations. Arterial Doppler ultrasound of the right lower limb showed an aneurysmal varix between the vein and the common femoral artery, confirming a diagnosis of Parkes-Weber syndrome. His maternal first cousin, 10 years his senior, also presented Parkes-Weber syndrome of the right upper limb.

DISCUSSION

This is the first observation of a familial case of Parkes-Weber syndrome in first cousins. Vascular malformations are transmitted in autosomal dominant fashion in the majority of infected families but with incomplete penetrance and variable expressivity. Symptoms appeared to worsen from generation to generation. In each generation of this family, we noted the presence of hemangiomas or capillary malformations with aggravation in the third generation and onset of Parkes-Weber syndrome. Genetic investigation with linkage analysis for the various members in order to identify a predisposing locus yielded little of interest.

Advances in Sturge-Weber syndrome

PURPOSE OF REVIEW

Recent neuroimaging, clinical and molecular neuropathologic studies have provided new insights into the neurologic aspects of Sturge-Weber syndrome and are summarized here.

RECENT FINDINGS

Molecular studies suggest that abnormal brain blood vessel vasoactive and extracellular matrix molecule expression, as well as aberrant brain vascular innervation, contribute to the vascular malformation and its consequences. New magnetic resonance sequences may be useful for the early diagnosis of Sturge-Weber syndrome and perfusion magnetic resonance imaging, single photon emission computed tomography imaging, and positron emission tomography imaging studies are suggesting that decreased brain blood flow combined with altered hemodynamics during prolonged seizures may contribute to the neurologic declines in Sturge-Weber syndrome.

SUMMARY

Recent advances in our understanding of the neurologic issues offer promise for preventing brain injury in Sturge-Weber syndrome. More research is needed to translate advances in molecular research and neuroimaging advances into new treatment strategies for the disease.

Peripheral vascular malformations: imaging, treatment approaches, and therapeutic issues

Peripheral vascular malformations are now described according to some accepted guidelines, and the principle of proper treatment (nidus ablation) is becoming clear. An appropriate classification scheme for vascular anomalies and definite indications for treatment are important to successful treatment overall. The findings from noninvasive imaging (ie, Doppler ultrasonography, computed tomography, or magnetic resonance imaging) in association with clinical findings are critical in establishing the diagnosis, evaluating the extent of the malformation, and planning appropriate treatment. Direct opacification of the nidus is useful, not only in making a correct diagnosis, but also in treating the lesion with sclerotherapy. In most cases, conservative treatment is recommended, but when a patient suffers clinical complications (eg, ulceration, pain, hemorrhage, cardiac failure, or unacceptable cosmetic consequences), the nidus sclerotherapy becomes mandatory. If the vascular malformation has blood outflow to a drainage vein during nidus opacification, flow control (with balloon occlusion, tourniquet, or embolization) is necessary to achieve sclerosant stasis within the nidus. Embolotherapy (with a coil, n-butyl cyanoacrylate, or small particles) should be used for subsequent multifaceted palliative therapy. A multi-disciplinary approach is needed in the treatment of a high-flow lesion, and a dedicated team approach is necessary for appropriate management in most cases.

Update on the molecular genetics of vascular anomalies

Genetic factors play a critical role in the pathogenesis of vascular anomalies. Significant advances have been made in recent years in identifying the genetic and molecular determinants of a variety of vascular anomalies using a molecular genetic approach. Several genes for vascular anomalies have been identified. These genes include AGGF1 for Klippel-Trenaunay syndrome, RASA1 for capillary malformations, KRIT1, MGC4607, PDCD10 for cerebral cavernous malformations, glomulin for glomuvenous malformations, TIE2 for multiple cutaneous and mucosal venous malformations, VEGFR-3, FOXC2, NEMO, SOX18 for lymphedema or related syndromes, ENG, ACVRLK1, MADH4 for HHT or related syndromes, NDP for Coats' disease, Notch3 for CADASIL, and PTEN for Proteus Syndrome. These findings have made genetic testing possible in some clinical cases, and may lead to the development of therapeutic strategies for vascular anomalies. Furthermore, these studies have identified critical genes involved in vascular morphogenesis, and provided fundamental understanding of the molecular mechanisms underlying vasculogenesis and angiogenesis.

Vascular update: Morphogenesis, tumors, malformations, and molecular dimensions

This vascular review is organized under the following headings: vasculogenesis and angiogenesis; vascular endothelial growth factors, their receptors, TIE receptors, and angiopoietins; other factors in blood vessel formation; parallel patterning in blood vessels and nerves; physiological and pathological neovascularization; the role of VEGF receptors in metastasis; anti-angiogenic therapy for tumors; association of blood vessels with fat; vascular malformations and vascular tumors; infantile hemangiomas; congenital hemangiomas; lymphatic malformations; molecular characteristics of some disorders with vascular malformations; Kasabach-Merritt phenomenon; Sturge-Weber syndrome, Klippel-Trenaunay syndrome, and Parkes Weber syndrome; diagnostic and laboratory studies; and future perspectives.

RASA1: variable phenotype with capillary and arteriovenous malformations

Capillary malformation-arteriovenous malformation (CM-AVM) is a newly discovered hereditary disorder. Its defining features are atypical cutaneous multifocal capillary malformations often in association with high-flow lesions: cutaneous, subcutaneous, intramuscular, intraosseous and cerebral arteriovenous malformations and arteriovenous fistulas. Some patients have Parkes Weber syndrome - a large congenital cutaneous vascular stain in an extremity, with bony and soft tissue hypertrophy and microscopic arteriovenous shunting. In the past, arteriovenous malformations and arteriovenous fistulas had been considered non-hereditary. A classical genetic approach was used to identify the locus. Candidate gene screening pinpointed mutations in RASA1 (p120-RASGAP) - a RasGTPase. RASA1 reverts active GTP-bound Ras into inactive GDP-bound form. Murine Rasa1 knockout and tetraploid-aggregated embryos with RNA interference exhibited abnormal vascular development. Lack of RASA1 activity caused inhibition of cell motility, possibly through p190-RhoGAP. Thus, RASA1 defects probably cause abnormal angiogenic remodeling of the primary capillary plexus that cannot be compensated for by other RasGAPs: RASA2, RASAL and NF1. Signaling pathways involving RASA1 might offer novel targets for treatment of high-flow vascular anomalies.

Venous angiomata: treatment with sclerosant foam

Venous angiomata, or venous malformations, are often present at birth, although they may not be evident until later. They consist of a spongy tangle of veins, and these lesions usually vary in size. Treatment of venous angiomata is often requested for cosmetic reasons, but painful ulcerations, nerve compression, functional disability can command care. This presentation describes management using sclerosant foam as the treating agent. During a 30-month period ending March 2004, 1,321 patients were investigated for venous disorders at the Vein Institute of La Jolla. Fourteen (incidence 1%) were found to have venous angiomata (: nine women). The age range was 15-76 years (mean 30.8 +/- 18.6). Lesions were classified by the Hamburg system and were primarily venous, extratruncular in 12 patients and combined extratruncular and truncular in two patients. Eight patients, three males, had manifestations of lower extremity Klippel-Trenaunay (syndrome; six had only venous angiomas. Only 10 of the 14 patients were treated. All patients were studied by Doppler duplex examination. Selected lesions were chosen for helical computed tomographic studies. Magnetic resonance venography was also used to image the lesions, define the deep circulation, note connections with normal circulation, identify vessels for therapeutic access, and determine infiltration of the lesion into adjacent soft tissue. Foam was produced by the Tessari two syringes one three-way stopcock teclinique, with the air to Polidocanol ratio being 4 or 5 to 1. This was used at 1% or 2% concentration, specific for each patient. The SonoSite 190 plus Duplex Doppler was used for ultrasound guidance, whenever deep access was required and to monitor progress and effects of treatment. A goal was set for each patient before treatment was begun. Ten patients were treated, and four await treatment. The mean number of treatments was 3.6 +/- 2.8 (range 1-10). A primary goal of pain-free healing was set in patients with nonhealing, painful ulceration or symptomatic varicose veins. This was achieved in all treated patients. Cosmetically, all of the patients were improved, and symptomatic patients were relieved of pain. The single complication was formation of a cutaneous ulcer following injection of telangiectasias. Sclerosant foam is a satisfactory tool to use in treating venous angiomata including the Klippel-Trenaunay syndrome. Use of foam sclerotherapy in this experience has proven the technique to be effective, essentially pain-free, and durable in the short term.

Basic science and clinical aspects of vascular anomalies

PURPOSE OF REVIEW

Patients with vascular and lymphatic anomalies are often 'medical orphans' ascertained through distinct medical specialists. Multidisciplinary vascular anomalies programs provide focused expertise in diagnosis and treatment for patients. National and international workshops on vascular anomalies are fostering clinical and basic science research to enhance our understanding of vascular development and vascular anomalies. Herewith is presented an update of recent advances in the study of vascular/lymphatic anomalies.

RECENT FINDINGS

New original findings include (1) the identification of distinct cell surface markers and other cellular properties in hemangiomas and vascular malformations relevant to vascular development, (2) the discovery of novel genetic mutations and susceptibility genes in patients with vascular anomalies, (3) recognition of new risk stratifications and clinical issues for patients with hemangiomas and vascular malformations, and (4) the elucidation of sequelae from the disorders as well as side effects of recent and previous therapies for vascular anomalies.

SUMMARY

Vascular anomalies are an attractive model for the study of human disorders of vasculogenesis and angiogenesis. The etiology of these disorders is unclear and likely represents a multifactorial process. Clinical clues are leading to scientific investigations that may enable targeted therapies, prevention strategies, or both.

Biomedicine and diseases: the Klippel-Trenaunay syndrome, vascular anomalies and vascular morphogenesis

Vascular morphogenesis is a vital process for embryonic development, normal physiologic conditions (e.g. wound healing) and pathological processes (e.g. atherosclerosis, cancer). Genetic studies of vascular anomalies have led to identification of critical genes involved in vascular morphogenesis. A susceptibility gene, VG5Q (formally named AGGF1), was cloned for Klippel-Trenaunay syndrome (KTS). AGGF1 encodes a potent angiogenic factor, and KTS-associated mutations enhance angiogenic activity of AGGF1, defining 'increased angiogenesis' as one molecular mechanism for the pathogenesis of KTS. Similar studies have identified other genes involved in vascular anomalies as important genes for vascular morphogenesis, including TIE2, VEGFR-3, RASA1, KRIT1, MGC4607, PDCD10, glomulin, FOXC2, NEMO, SOX18, ENG, ACVRLK1, MADH4, NDP, TIMP3, Notch3, COL3A1 and PTEN. Future studies of vascular anomaly genes will provide insights into the molecular mechanisms for vascular morphogenesis, and may lead to the development of therapeutic strategies for treating these and other angiogenesis-related diseases, including coronary artery disease and cancer.

[Capillary malformations associated with cerebral cavernous malformation]

INTRODUCTION

Capillary malformations such as benign hereditary telangiectasia are a familial affection, of dominant autosomal transmission, characterized by the progressive development of cutaneous telangiectasia during childhood. The association with cutaneous vascular, arteriovenous or lymphatic malformations is exceptional and has only recently been described.

CASE REPORT

A 5 year-old girl presented with widespread erythematous, predominantly telangiectasic, congenital and acquired macules when she was one year-old. Her history was marked by right temporal cerebral hemorrhage at the age of 4, revealing a right temporal cavernoma-like vascular malformation. The familial history of telangiectasic macules and clinical and histological examination led to the diagnosis of benign hereditary telangiectasia.

DISCUSSION

This case report raises doubt on the exclusively cutaneous nature of benign hereditary telangiectasic-type capillary malformations. Moreover, it illustrates the possibility of a particular clinical form of this affection, associating classical telangiectasia and post-wine stain-type macules. The recent localization of the locus implied in this affection in 5q14 in the same chromosomic space as the CMC1 locus incriminated in familial capillary malformations, suggests that these two affections are in fact phenotype variations of a single and same clinical entity.

Increased expression of osteopontin gene in atypical teratoid/rhabdoid tumor of the central nervous system

The atypical teratoid/rhabdoid tumor, primary to the central nervous system, is a highly malignant and aggressive neoplasm of infancy and childhood. Although having distinct biological features and clinical outcomes, it is frequently misdiagnosed as primitive neuroectodermal tumor/medulloblastoma. To further distinguish the underlying pathogenesis and to identify biological markers for clinical use, an atypical teratoid/rhabdoid tumor-derived cell line was established and its gene expression pattern analyzed in comparison to the human astrocyte SVG12 cell line and the human DAOY medulloblastoma cell line using a complementary DNA microarray method. The osteopontin gene was found specifically upregulated in atypical teratoid/rhabdoid tumor cells. This specificity was confirmed by immunohistochemistry in pathological sections of tissues from atypical teratoid/rhabdoid tumor patients. Even though the role of osteopontin in the cytopathogenesis of atypical teratoid/rhabdoid tumor still needs to be determined, our data support that overexpressed osteopontin is a potential diagnostic marker for atypical teratoid/rhabdoid tumor.

GAP control: regulating the regulators of small GTPases

The small GTPases of the Ras superfamily mediate numerous biological processes through their ability to cycle between an inactive GDP-bound and an active GTP-bound form. Among the key regulators of GTPase cycling are the GTPase-activating proteins (GAPs), which stimulate the weak intrinsic GTP-hydrolysis activity of the GTPases, thereby inactivating them. Despite the abundance of GAPs and the fact that mutations in GAP-encoding genes underlie several human diseases, these proteins have received relatively little attention. Recent studies have addressed the regulatory mechanisms that influence GAP activity. So far, findings suggest that GAP activity is regulated by several mechanisms, including protein-protein interactions, phospholipid interactions, phosphorylation, subcellular translocation and proteolytic degradation.

Hereditary Vascular Anomalies

Increased understanding of the mechanisms of angiogenesis and lymphangiogenesis has provided a glimpse at some of the molecules involved in the pathophysiology of hemangiomas and vascular malformations. This review focuses on recent advances in our understanding of the mechanisms of angiogenesis/lymphangiogenesis and the differentiation of arterial, venous, and lymphatic vessels. We integrate this knowledge with new data obtained from genetic studies in humans, which have revealed a number of heretofore-unsuspected candidates involved in the development of familial vascular anomalies. We present a common infantile vascular tumor, hemangioma, and then focus on hereditary familial vascular and lymphatic malformations. We also summarize transgenic mouse models for some of these malformations. It seems reasonable to believe that novel therapeutic strategies will soon emerge for the treatment of hemangiomas and vascular malformations.

Sturge-Weber syndrome

Sturge-Weber syndrome is a sporadic neurocutaneous disease characterized by facial port-wine stain, ocular abnormalities (glaucoma and choroidal hemangioma) and leptomeningeal angioma. Although the precise pathogenesis is unknown, available data regarding genetics, embryogenesis, and pathologic features are briefly reviewed. Clinical features vary from mild incomplete forms to full-blown disease with facial stain, seizures, and glaucoma. Frequencies of associated complications are reviewed. To plan treatment and further follow-up, diagnosis of glaucoma and intracranial involvement, even if asymptomatic, is fundamental in children at risk. Early neuroimaging features are important to recognize. Management of patients with Sturge-Weber syndrome is focused on treating associated neurologic and ocular abnormalities.