Parkes Weber syndrome associated with two somatic pathogenic variants in RASA1

Pseudoaneurysm formation after embolization of giant arteriovenous malformation of the lower limb associated with Parkes Weber syndrome: A case report and literature review

A 63-year-old woman presented with a giant arteriovenous malformation (AVM) of the lower limbs associated with Parkes Weber syndrome (PWS). The AVM was supplied by 4 branches of the right profunda femoris artery and 4-stage embolization was performed. At 67 years of age, she developed a pseudoaneurysm due to the recanalization of a coiled profunda femoris artery branch arterial aneurysm. We performed re-embolization of the coiled profunda femoris artery and observed its shrinkage, but 2 months later, the pseudoaneurysm began to expand again, having a fatal course. This case indicates that battles against giant AVM-associated PWS follow a long and convoluted path. We present this case with reviewing 15 previously reported cases to improve our management of PWS.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

Investigation of the Genetic Determinants of Telangiectasia and Solid Organ Arteriovenous Malformation Formation in Hereditary Hemorrhagic Telangiectasia (HHT)

Telangiectases and arteriovenous malformations (AVMs) are the characteristic lesions of Hereditary Hemorrhagic Telangiectasia (HHT). Somatic second-hit loss-of-function variations in the HHT causative genes, ENG and ACVRL1, have been described in dermal telangiectasias. It is unclear if somatic second-hit mutations also cause the formation of AVMs and nasal telangiectasias in HHT. To investigate the genetic mechanism of AVM formation in HHT, we evaluated multiple affected tissues from fourteen individuals. DNA was extracted from fresh/frozen tissue of 15 nasal telangiectasia, 4 dermal telangiectasia, and 9 normal control tissue biopsies, from nine unrelated individuals with HHT. DNA from six formalin-fixed paraffin-embedded (FFPE) AVM tissues (brain, lung, liver, and gallbladder) from five individuals was evaluated. A 736 vascular malformation and cancer gene next-generation sequencing (NGS) panel was used to evaluate these tissues down to 1% somatic mosaicism. Somatic second-hit mutations were identified in three in four AVM biopsies (75%) or half of the FFPE (50%) samples, including the loss of heterozygosity in ENG in one brain AVM sample, in which the germline mutation occurred in a different allele than a nearby somatic mutation (both are loss-of-function mutations). Eight of nine (88.9%) patients in whom telangiectasia tissues were evaluated had a somatic mutation ranging from 0.68 to 1.96% in the same gene with the germline mutation. Six of fifteen (40%) nasal and two of four (50%) dermal telangiectasia had a detectable somatic second hit. Additional low-level somatic mutations in other genes were identified in several telangiectasias. This is the first report that nasal telangiectasias and solid organ AVMs in HHT are caused by very-low-level somatic biallelic second-hit mutations.

DVA: predicting the functional impact of single nucleotide missense variants

BACKGROUND

In the past decade, single nucleotide variants (SNVs) have been identified as having a significant relationship with the development and treatment of diseases. Among them, prioritizing missense variants for further functional impact investigation is an essential challenge in the study of common disease and cancer. Although several computational methods have been developed to predict the functional impacts of variants, the predictive ability of these methods is still insufficient in the Mendelian and cancer missense variants.

RESULTS

We present a novel prediction method called the disease-related variant annotation (DVA) method that predicts the effect of missense variants based on a comprehensive feature set of variants, notably, the allele frequency and protein-protein interaction network feature based on graph embedding. Benchmarked against datasets of single nucleotide missense variants, the DVA method outperforms the state-of-the-art methods by up to 0.473 in the area under receiver operating characteristic curve. The results demonstrate that the proposed method can accurately predict the functional impact of single nucleotide missense variants and substantially outperforms existing methods.

CONCLUSIONS

DVA is an effective framework for identifying the functional impact of disease missense variants based on a comprehensive feature set. Based on different datasets, DVA shows its generalization ability and robustness, and it also provides innovative ideas for the study of the functional mechanism and impact of SNVs.

Parkes Weber syndrome: a rare cause of foot drop

This case report describes a patient in her late 60s, previously diagnosed with Klippel-Trenaunay syndrome who presented with difficulty walking. A year prior to her presentation she had a fall which made her notice a painless foot drop on the right. Her right leg was profoundly hypertrophied compared with the left, and a port-wine stain was present on the lateral side, extending from the hip to the mid-shin. The patient's differential diagnosis based on clinical examination and investigations is discussed leading to a final diagnosis of sciatic neuropathy secondary to an arteriovenous malformation due to Parkes Weber syndrome.

Current concepts of vascular anomalies

Vascular anomalies encompass a variety of malformations and tumors that can result in severe morbidity and mortality in both adults and children. Advances have been made in the classification and diagnosis of these anomalies, with the International Society for the Study of Vascular Anomalies establishing a widely recognized classification system. In recent years, notable progress has been made in genetic testing and imaging techniques, enhancing our ability to diagnose these conditions. The increasing sophistication of genetic testing has facilitated the identification of specific genetic mutations that help treatment decisions. Furthermore, imaging techniques such as magnetic resonance imaging and computed tomography have greatly improved our capacity to visualize and detect vascular abnormalities, enabling more accurate diagnoses. When considering reconstructive surgery for facial vascular anomalies, it is important to consider both functional and cosmetic results of the procedure. Therefore, a comprehensive multidisciplinary approach involving specialists from dermatology, radiology, and genetics is often required to ensure effective management of these conditions. Overall, the treatment approach for facial vascular anomalies depends on the type, size, location, and severity of the anomaly. A thorough evaluation by a team of specialists can determine the most appropriate and effective treatment plan.

Genotypes and phenotypes heterogeneity in PIK3CA-related overgrowth spectrum and overlapping conditions: 150 novel patients and systematic review of 1007 patients with PIK3CA pathogenetic variants

BACKGROUND

Postzygotic activating PIK3CA variants cause several phenotypes within the PIK3CA-related overgrowth spectrum (PROS). Variant strength, mosaicism level, specific tissue involvement and overlapping disorders are responsible for disease heterogeneity. We explored these factors in 150 novel patients and in an expanded cohort of 1007 PIK3CA-mutated patients, analysing our new data with previous literature to give a comprehensive picture.

METHODS

We performed ultradeep targeted next-generation sequencing (NGS) on DNA from skin biopsy, buccal swab or blood using a panel including phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway genes and GNAQ, GNA11, RASA1 and TEK. Additionally, 914 patients previously reported were systematically reviewed.

RESULTS

93 of our 150 patients had PIK3CA pathogenetic variants. The merged PROS cohort showed that PIK3CA variants span thorough all gene domains, some were exclusively associated with specific PROS phenotypes: weakly activating variants were associated with central nervous system (CNS) involvement, and strongly activating variants with extra-CNS phenotypes. Among the 57 with a wild-type PIK3CA allele, 11 patients with overgrowth and vascular malformations overlapping PROS had variants in GNAQ, GNA11, RASA1 or TEK.

CONCLUSION

We confirm that (1) molecular diagnostic yield increases when multiple tissues are tested and by enriching NGS panels with genes of overlapping 'vascular' phenotypes; (2) strongly activating PIK3CA variants are found in affected tissue, rarely in blood: conversely, weakly activating mutations more common in blood; (3) weakly activating variants correlate with CNS involvement, strong variants are more common in cases without; (4) patients with vascular malformations overlapping those of PROS can harbour variants in genes other than PIK3CA.

A comparison on predicting functional impact of genomic variants

Single-nucleotide polymorphism (SNPs) may cause the diverse functional impact on RNA or protein changing genotype and phenotype, which may lead to common or complex diseases like cancers. Accurate prediction of the functional impact of SNPs is crucial to discover the ‘influential’ (deleterious, pathogenic, disease-causing, and predisposing) variants from massive background polymorphisms in the human genome. Increasing computational methods have been developed to predict the functional impact of variants. However, predictive performances of these computational methods on massive genomic variants are still unclear. In this regard, we systematically evaluated 14 important computational methods including specific methods for one type of variant and general methods for multiple types of variants from several aspects; none of these methods achieved excellent (AUC ≥ 0.9) performance in both data sets. CADD and REVEL achieved excellent performance on multiple types of variants and missense variants, respectively. This comparison aims to assist researchers and clinicians to select appropriate methods or develop better predictive methods.

Parkes Weber syndrome with lymphedema caused by a somatic KRAS variant

Parkes Weber syndrome is a vascular malformation overgrowth condition typically involving the legs. Its main features are diffuse arteriovenous fistulas and enlargement of the limb. The condition has been associated with pathogenic germline variants in RASA1 and EPHB4. We report two individuals with Parkes Weber syndrome of the leg and primary lymphedema containing a somatic KRAS variant (NM_004985.5:c.35G > A; p.Gly12Asp). KRAS variants, which cause somatic intracranial and extracranial arteriovenous malformations, also result in Parkes Weber syndrome with lymphatic malformations.

Mosaic RASopathy due to KRAS variant G12D with segmental overgrowth and associated peripheral vascular malformations

Oncogenic RAS variants lead to constitutive overactivation and increased signal transduction into downstream pathways. They are found as somatic driver events in various types of human cancer. In a somatic mosaic status, the same RAS variants have been associated with a wide spectrum of focal or segmental tissue dysplasia and overgrowth including various types of congenital nevi, vascular malformations, and other changes (mosaic RASopathies). We present a 3-year-old male patient with segmental overgrowth of the subcutaneous fatty tissue of the right lower extremity with colocalized arteriovenous and capillary malformations and dysplastic draining veins in combination with talipes equinovarus of the right foot. In tissue biopsies of the affected extremity, we identified a mosaic KRAS variant, c.35G>A (p.Gly12Asp), while this variant was absent in the DNA extracted from a biopsy of the normal extremity. This report provides further evidence for the wide clinical and phenotypic variability associated with mosaic KRAS variants. The described pattern confirms that the combination of segmental overgrowth and vascular anomalies in the form of arteriovenous and capillary malformations is a possible manifestation of a mosaic RASopathy. The accurate genetic diagnosis is crucial for molecular-targeted therapy, which might be a future therapeutic target for mosaic RASopathies.