Somatic Mutational Landscape of Extracranial Arteriovenous Malformations and Phenotypic Correlations

Extracranial Vascular Anomalies Driven by RAS/MAPK Variants: Spectrum and Genotype-Phenotype Correlations

BACKGROUND

We aimed to correlate alterations in the rat sarcoma virus (RAS)/mitogen-activated protein kinase pathway in vascular anomalies to the clinical phenotype for improved patient and treatment stratification.

METHODS AND RESULTS

This retrospective multicenter cohort study included 29 patients with extracranial vascular anomalies containing mosaic pathogenic variants (PVs) in genes of the RAS/mitogen-activated protein kinase pathway. Tissue samples were collected during invasive treatment or clinically indicated biopsies. PVs were detected by the targeted sequencing of panels of genes known to be associated with vascular anomalies, performed using DNA from affected tissue. Subgroup analyses were performed according to the affected genes with regard to phenotypic characteristics in a descriptive manner. Twenty-five vascular malformations, 3 vascular tumors, and 1 patient with both a vascular malformation and vascular tumor presented the following distribution of PVs in genes: Kirsten rat sarcoma viral oncogene (n=10), neuroblastoma ras viral oncogene homolog (n=1), Harvey rat sarcoma viral oncogene homolog (n=5), V-Raf murine sarcoma viral oncogene homolog B (n=8), and mitogen-activated protein kinase kinase 1 (n=5). Patients with RAS PVs had advanced disease stages according to the Schobinger classification (stage 3-4: RAS, 9/13 versus non-RAS, 3/11) and more frequent progression after treatment (RAS, 10/13 versus non-RAS, 2/11). Lesions with Kirsten rat sarcoma viral oncogene PVs infiltrated more tissue layers compared with the other PVs including other RAS PVs (multiple tissue layers: Kirsten rat sarcoma viral oncogene, 8/10 versus other PVs, 6/19).

CONCLUSIONS

This comparison of patients with various PVs in genes of the RAS/MAPK pathway provides potential associations with certain morphological and clinical phenotypes. RAS variants were associated with more aggressive phenotypes, generating preliminary data and hypothesis for future larger studies.

Medical Management and Therapeutic Updates on Vascular Anomalies of the Head and Neck: Part 2

Discovery of inherited and somatic genetic mutations, along with advancements in clinical and scientific research, has improved understanding of vascular anomalies and changed the treatment paradigm. With aim of minimizing need for invasive procedures and improving disease outcomes, molecularly targeted medications and anti-angiogenesis agents have become important as both adjuncts to surgery, and increasingly, as the primary treatment of vascular anomalies. This article highlights the commonly used and emerging therapeutic medications for non-malignant vascular tumors and vascular malformations in addition to medical management of associated hematologic abnormalities.

Genetic mutations and phenotype characteristics in peripheral vascular malformations: A systematic review

Vascular malformations (VMs) are clinically diverse with regard to the vessel type, anatomical location, tissue involvement and size. Consequently, symptoms and disease impact differ significantly. Diverse causative mutations in more and more genes are discovered and play a major role in the development of VMs. However, the relationship between the underlying causative mutations and the highly variable phenotype of VMs is not yet fully understood. In this systematic review, we aimed to provide an overview of known causative mutations in genes in VMs and discuss associations between the causative mutations and clinical phenotypes. PubMed and EMBASE libraries were systematically searched on November 9th, 2022 for randomized controlled trials and observational studies reporting causative mutations in at least five patients with peripheral venous, lymphatic, arteriovenous and combined malformations. Study quality was assessed with the Newcastle-Ottawa Scale. Data were extracted on patient and VM characteristics, molecular sequencing method and results of molecular analysis. In total, 5667 articles were found of which 69 studies were included, reporting molecular analysis in a total of 4261 patients and 1686 (40%) patients with peripheral VMs a causative mutation was detected. In conclusion, this systematic review provides a comprehensive overview of causative germline and somatic mutations in various genes and associated phenotypes in peripheral VMs. With these findings, we attempt to better understand how the underlying causative mutations in various genes contribute to the highly variable clinical characteristics of VMs. Our study shows that some causative mutations lead to a uniform phenotype, while other causal variants lead to more varying phenotypes. By contrast, distinct causative mutations may lead to similar phenotypes and result in almost indistinguishable VMs. VMs are currently classified based on clinical and histopathology features, however, the findings of this systematic review suggest a larger role for genotype in current diagnostics and classification.

Lower-Extremity Arteriovenous Malformation Masquerading as Peripheral Artery Disease

An arteriovenous malformation (AVM) refers to an anomalous, direct connection between an artery and a vein. Typically, these two vessels are interposed by high-resistance capillary beds, the absence of which results in a high-flow system from an artery into a vein. Venous vessel walls are not designed to handle such high-pressure blood flow, and their vessel wall structure becomes permanently altered and weakened. For this reason, AVMs are at an increased risk for hemorrhages and ruptures. AVMs present with a spectrum of symptoms, ranging from skin discoloration, ischemia in distal tissues, and heart failure from arteriovenous shunting. Here, we present a case of a patient who underwent amputation of his second left toe, initially thought to be a result of peripheral arterial disease (PAD) due to his extensive smoking history. Further imaging findings revealed a rare lower-extremity AVM as the source of his ischemia, not PAD. Ultimately, the treatment of the vascular anomaly and resolution of the patient's symptoms were achieved via transarterial embolization. This case emphasizes the importance of looking beyond PAD as the cause of distal lower-extremity ischemia and provides insights into an uncommon and often missed diagnosis of extracranial AVMs.

Extracranial arteriovenous malformations demonstrate dysregulated TGF-β/BMP signaling and increased circulating TGF-β1

Extracranial arteriovenous malformations (AVMs) are characterized by anomalous arterial-to-venous connections, aberrant angiogenesis, local inflammation and hypoxia, and disorganized histological architecture; however, the precise molecular perturbations leading to this phenotype remain elusive. We hypothesized that extracranial AVM tissue would demonstrate deregulation of the TGF-β/BMP signaling pathway, which may serve as a potential target in the development of molecular-based therapies for AVMs. AVM tissue was harvested during resection from 10 patients with AVMs and compared to control tissue. Blood was collected from 14 AVM patients and 10 patients without AVMs as controls. Expression of TGF-β/BMP pathway components was analyzed using RT-PCR, western blotting, and immunohistochemistry. Circulating levels of TGF-β1 were analyzed by ELISA. Paired t tests were utilized to perform statistical analysis. The mRNA levels of TGF-β1, ALK1, Endoglin (ENG), Smad6, Smad7, and Smad8 were significantly elevated in AVM tissue when compared to controls. Protein levels of TGF-β1 and Smad3 were elevated in AVM tissue while protein levels of BMP-9, ALK1, Smad1, Smad6, and Smad8 were significantly decreased in AVMs. Immunohistochemistry demonstrated increased TGF-β1 in the perivascular cells of AVMs compared to normal controls, and circulating levels of TGF-β1 were significantly higher in AVM patients. Patients with AVMs demonstrate aberrant TGF-β/BMP expression in AVM tissue and blood compared to controls. Targeting aberrantly expressed components of the TGF-β/BMP pathway in extracranial AVMs may be a viable approach in the development of novel molecular therapies, and monitoring circulating TGF-β1 levels may be a useful indicator of treatment success.

Genetic understanding of vascular anomalies: better classification and risk-stratification with targeted therapeutic options - a new horizon for vascular anomaly patients

Linked article: F.N. El Sissy et al. J Eur Acad Dermatol Venereol 2022; 36: 905–912. https://doi.org/10.1111/jdv.18046.