Francine Blei

Somatic mutation of vascular endothelial growth factor receptors in juvenile hemangioma

Juvenile hemangiomas are the most common tumors of infancy, occurring in as many as 10% of all births. These benign vascular lesions enlarge rapidly during the first year of life by hyperplasia of endothelial cells and attendant pericytes and then spontaneously involute over a period of years, leaving loose fibrofatty tissue. Several hypotheses have been put forth concerning hemangiogenesis, including the possibility that the tumor is the result of somatic mutation in one or more components of critical vascular growth‐regulatory pathways. To test this hypothesis, we obtained 15 proliferative‐phase hemangiomas after surgical resection and dissected them to enrich for the lesional (endothelial and pericytic) components of each specimen. To determine whether hemangiomas represent a clonal expansion from a single progenitor cell, we assayed X‐inactivation patterns for each lesion by using the polymorphic X‐linked human androgen receptor gene. Twelve of 14 informative hemangiomas showed a significant degree of allelic loss after methylation‐based and transcription‐based polymerase chain reaction clonality assays, suggesting a nonrandom X‐inactivation pattern and, thus, a monoclonal origin. We then sequenced genes encoding the receptors of the vascular endothelial growth factors (VEGFs) as candidates for potential somatic mutation. Mutations were found in two of the 15 hemangioma specimens: a missense mutation (P1147S) in the kinase domain of the VEGFR2 (FLK1/KDR) gene in one specimen and a missense mutation (P954S) in the kinase insert of the VEGFR3 (FLT4) gene in another specimen. In each case, the mutation was detected in tumor tissue but not in adjacent normal tissue. These results suggest that one potential mechanism involved in hemangioma formation is the alteration of the VEGF signaling pathway in endothelial and/or pericytic cells.

Genetic mapping of a novel familial form of infantile hemangioma

Infantile hemangiomas are the most common tumor of infancy, occurring with an incidence of up to 10% of all births. They are benign but highly proliferative lesions involving aberrant localized growth of capillary endothelium. Although most hemangiomas occur sporadically and as single lesions, or in conjunction with pleiotropic genetic syndromes, we have previously identified six kindreds where hemangiomas appear to segregate as an autosomal dominant trait with high penetrance. Four such families contain affected individuals in three or more generations. In the current study, blood samples from five of these families were collected and used in a whole genome linkage search at 10-cM resolution. We established evidence for linkage to 5q in three families, and evidence for locus heterogeneity. The three 5q-linked families were further genotyped to generate haplotype information and narrow the candidate interval. Based on recombination breakpoint analysis, the interval exists between markers D5S2490 and D5S408, spanning 55 cM, and corresponding to 5q31-33. Using information from affected and unaffected individuals, the interval spans 38 cM between markers D5S1469 and D5S211. Three candidate genes involved with blood vessel growth map to this region: fibroblast growth factor receptor-4 (FGFR4), platelet-derived growth factor receptor-beta (PDG-FRB), and fms-related tyrosine kinase-4 (FLT4). The genes and gene products associated with familial hemangiomas may be involved somatically in the more common sporadic cases.

Growth factor control of extracellular proteolysis

The involvement of proteases and growth factors in angiogenesis is complex. The angiogenic factor basic fibroblast growth factor (bFGF) induces increased synthesis of both plasminogen activator and collagenase in endothelial cells. In addition, bFGF increases the number of plasminogen activator receptors on the cell surface. Increased production of plasmin may be responsible for the release of soluble complexes of heparan sulfate-bFGF which may be the active form of bFGF. The activity of a negative regulator of angiogenesis, transforming growth factor beta (TGF-beta), is also regulated by proteases since the released latent form of TGF-beta is activated by a surface proteolytic assembly plasminogen activator and plasmin. Since TGF-beta induces an inhibitor of plasminogen activator, the activation reaction is self-regulatory.

Consensus-Derived Practice Standards Plan for Complicated Kaposiform Hemangioendothelioma

Kaposiform hemangioendothelioma (KHE) is a rare, potentially life-threatening vascular tumor often associated with a coagulopathy known as Kasabach– Merritt phenomenon (KMP). 1 Optimal therapy for KHE is not known, and despite well-published classification systems, physicians still confuse this entity with other vascular anomalies. In the interest of standardizing clinical practice across specialties and institutions and to establish a basis for the design of comparative effectiveness studies in vascular tumors, we have developed a consensus-derived standard of practice for the treatment of KHE with and without associated KMP. Vascularanomaliesencompassaheterogeneousgroupoftumors and malformations characterized by the presence of abnormal vascular structures. Vascular anomalies most often occurintheskinandsofttissue;however,theycanoccurwithin any organ and present with a wide range of symptoms and complications, depending on the type and location of the lesion(s). As a result of the heterogeneity of clinical presentations, patients have traditionally been referred to both adult and pediatric specialists in dermatology, hematology/oncology,interventionalradiology,surgery,plasticsurgery,ophthalmology, and/or otolaryngology to address a particular clinical problem. This type of “problem-driven” care has resulted in patients being seen by multiple specialists without a cohesive understanding of the natural history or mechanism of disease. The formation of interdisciplinary vascular anomalies centershas advanced our ability todiagnose and classify these conditions; however, standardized treatment protocols and assessment of response criteria do not currently exist. Clinicians rely on case reports, limited retrospective series, and expert opinion when selecting therapeutic interventions for complicated patients. This knowledge gap underscores the importance of gaining consensus in the treatment of these rare, often life-threatening anomalies. Consensus will limit practice variability and will allow comparison of data across institutions and subspecialties and facilitate the development of evidence-based practice standards.

RASA1 mutations and associated phenotypes in 68 families with capillary malformation-arteriovenous malformation

Capillary malformation–arteriovenous malformation (CM–AVM) is an autosomal‐dominant disorder, caused by heterozygous RASA1 mutations, and manifesting multifocal CMs and high risk for fast‐flow lesions. A limited number of patients have been reported, raising the question of the phenotypic borders. We identified new patients with a clinical diagnosis of CM–AVM, and patients with overlapping phenotypes. RASA1 was screened in 261 index patients with: CM–AVM (n = 100), common CM(s) (port‐wine stain; n = 100), Sturge–Weber syndrome (n = 37), or isolated AVM(s) (n = 24). Fifty‐eight distinct RASA1 mutations (43 novel) were identified in 68 index patients with CM–AVM and none in patients with other phenotypes. A novel clinical feature was identified: cutaneous zones of numerous small white pale halos with a central red spot. An additional question addressed in this study was the “second‐hit” hypothesis as a pathophysiological mechanism for CM–AVM. One tissue from a patient with a germline RASA1 mutation was available. The analysis of the tissue showed loss of the wild‐type RASA1 allele. In conclusion, mutations in RASA1 underscore the specific CM–AVM phenotype and the clinical diagnosis is based on identifying the characteristic CMs. The high incidence of fast‐flow lesions warrants careful clinical and radiologic examination, and regular follow‐up.

Successful multimodal therapy for kaposiform hemangioendothelioma complicated by Kasabach-Merritt phenomenon: case report and review of the literature.

We present the management challenge provided by a patient with kaposiform hemangioendothelioma associated with Kasabach-Merritt phenomenon. A female child presented at 14 months of age with an ecchymotic swelling of her right upper arm and axilla. Subsequently, she developed profound thrombocytopenia and hypofibrinogenemia (Kasabach-Merritt phenomenon). Biopsy of the lesion revealed kaposiform hemangioendothelioma, which has been reported as the predominant pathologic diagnosis associated with Kasabach-Merritt phenomenon. To achieve involution of the lesion and preserve function of the arm, the following interventions were involved: embolization, systemic interferon, cyclophosphamide, epsilon aminocaproic acid, and compression therapy. The clinical management of this patient was formidable until we arrived at the proper combination of therapies. Multimodal intervention may be required to manage fastidious hemangioendotheliomas of childhood, achieve clinical improvement, and prevent further morbidity.

Periocular hemangiomas: what every physician should know.

Abstract:  Hemangiomas are the most common benign tumor of infancy. Most hemangiomas remain asymptomatic and can be managed by close observation; however, immediate treatment is indicated for hemangiomas that may cause significant complications. Periocular hemangiomas warrant close evaluation and early, active treatment of those with the potential to threaten or permanently compromise vision. Herein we review the clinical features of periocular hemangiomas, differential diagnosis, possible ophthalmologic complications and sequelae, and therapeutic modalities.

Increased circulating AC133+ CD34+ endothelial progenitor cells in children with hemangioma.

UNLABELLED Hemangioma is the most common soft-tissue tumor of infancy. Despite the frequency of these vascular tumors, the origin of hemangioma-endothelial cells is unknown. Circulating endothelial progenitor cells (EPCs) have recently been identified as vascular stem cells with the capacity to contribute to postnatal vascular development. We have attempted to determine whether circulating EPCs are increased in hemangioma patients and thereby provide insight into the role of EPCs in hemangioma growth. METHODS AND RESULTS Peripheral blood mononuclear cells (PBMCs) were isolated from hemangioma patients undergoing surgical resection (N = 5) and from age-matched controls (N = 5) undergoing strabismus correction surgery. PBMCs were stained with fluorescent-labeled antibodies for AC133, CD34, and VEGFR2/KDR. Fluorescent-labeled isotype antibodies served as negative controls. Histologic sections of surgical specimens were stained with the specific hemangioma markers Glut1, CD32, and merosin, to confirm the diagnosis of common hemangioma of infancy. EPCs harvested from healthy adult volunteers were stained with Glut1, CD32, and merosin, to assess whether cultured EPCs express known hemangioma markers. Hemangioma patients had a 15-fold increase in the number of circulating CD34 AC133 dual-staining cells relative to controls (0.78+/-0.14% vs.0.052+/-0.017%, respectively). Similarly, the number of PBMCs that stained positively for both CD34 and KDR was also increased in hemangioma patients (0.49+/-0.074% vs. 0.19+/-0.041% in controls). Cultured EPCs stained positively for the known hemangioma markers Glut1, CD32, merosin. CONCLUSIONS This is the first study to suggest a role for EPCs in the pathogenesis of hemangioma. Our results imply that increased levels of circulating EPCs may contribute to the formation of this vascular tumor.

Rapidly involuting congenital haemangioma associated with transient thrombocytopenia and coagulopathy: a case series.

Rapidly involuting congenital haemangioma (RICH) may present with thrombocytopenia, low fibrinogen and elevated fibrin degradation products and D‐dimers. Such complications have rarely been reported. We wished to define the clinical characteristics of the thrombocytopenia and coagulopathy associated with RICH, to emphasize the transient nature of this haematological complication and to distinguish these abnormalities from true Kasabach–Merritt phenomenon (KMP). We present a case series of seven patients with large RICH who presented with thrombocytopenia and coagulopathy during the first week of life. Clinical and haematological characteristics were recorded retrospectively. Two of the patients were treated with embolization due to early signs of high‐output cardiac failure; four patients received oral corticosteroids in the range of 2 mg kg−1 daily; one patient did not receive any treatment in the neonatal period, although the tumour was excised at 6 months of age. Two patients with platelet counts lower than 10 × 109 L−1 received a platelet transfusion. There were no bleeding complications and only one patient presented with petechiae. In all seven patients, platelet counts started to increase at > 2 weeks of age and the coagulopathy resolved. We conclude that RICH may present with thrombocytopenia and coagulopathy similar to mild KMP early in the neonatal period. However, in contrast to true KMP, these abnormal laboratory findings are self‐limited and are usually not complicated by bleeding problems.

Evidence for loss of heterozygosity of 5q in sporadic haemangiomas: are somatic mutations involved in haemangioma formation?

Background/Aims—Haemangiomas are common benign tumours of infancy that consist of rapidly proliferating endothelial cells. A locus for an autosomal dominant predisposition to haemangioma has been identified recently on chromosome 5q. This study aimed to investigate loss of heterozygosity on chromosomes 5 and 9 in haemangiomas. Methods—Sporadic proliferative phase haemangiomas were microdissected. Polymerase chain reaction amplification and analysis of microsatellite markers on chromosomes 5 and 9 was carried out. Results—There was a significant loss of heterozygosity for markers on chromosome 5q in haemangioma tissue, when compared with either markers from chromosome 5p (p < 0.05) or markers from chromosome 9 (p < 0.05). Conclusions—These results suggest that haemangioma formation might be associated with somatic mutational events, and provides evidence that a locus on 5q is involved in the formation of sporadic haemangiomas.