Segmental undergrowth is associated with pathogenic variants in vascular malformation genes: A retrospective case-series study

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.

Molecular Basis and Diagnostic Approach to Isolated and Syndromic Lateralized Overgrowth in Childhood

OBJECTIVE

To demonstrate a high-yield molecular diagnostic workflow for lateralized overgrowth (LO), a congenital condition with abnormal enlargement of body parts, and to classify it by molecular genetics. and STUDY DESIGN: We categorized 186 retrospective cases of LO diagnosed between 2003 and 2023 into suspected Beckwith-Wiedemann spectrum (BWSp), PIK3CA-Related Overgrowth Spectrum (PROS), vascular overgrowth (VO) , or isolated (ILO), based on initial clinical assessments, to determine the appropriate first-tier molecular tests and tissue for analysis. Patients underwent testing for 11p15 epigenetic abnormalities or somatic variants in genes related to PI3K/AKT/mTOR, vascular proliferation, and RAS-MAPK cascades using blood or skin DNA. For cases with negative initial tests, a sequential cascade molecular approach was employed to improve diagnostic yield.

RESULTS

This approach led to a molecular diagnosis in 54% of cases, 89% of cases consistent with initial clinical suspicions and 11% reclassified. BWSp was the most common cause, with 43% of cases exhibiting 11p15 abnormalities. PROS had the highest confirmation rate, with 74% of clinically diagnosed patients showing a PIK3CA variant. VO demonstrated significant clinical overlap with other syndromes. Molecular diagnosis of ILO proved challenging, with only 21% of cases classifiable into a specific condition.

CONCLUSION

Despite, LO is underdiagnosed from a molecular viewpoint and to date has had no diagnostic guidelines, which would be crucial for addressing potential cancer predisposition, enabling precision medicine treatments, or guiding management. This study sheds light on the molecular etiology of LO, highlighting the importance of tailored diagnostic approach and of selecting appropriate testing to achieve the highest diagnostic yield.

Capillary malformations

Capillary malformation (CM), or port wine birthmark, is a cutaneous congenital vascular anomaly that occurs in 0.1%-2% of newborns. Patients with a CM localized on the forehead have an increased risk of developing a neurocutaneous disorder called encephalotrigeminal angiomatosis or Sturge-Weber syndrome (SWS), with complications including seizure, developmental delay, glaucoma, and vision loss. In 2013, a groundbreaking study revealed causative activating somatic mutations in the gene (GNAQ) encoding guanine nucleotide-binding protein Q subunit α (Gαq) in CM and SWS patient tissues. In this Review, we discuss the disease phenotype, the causative GNAQ mutations, and their cellular origin. We also present the endothelial Gαq-related signaling pathways, the current animal models to study CM and its complications, and future options for therapeutic treatment. Further work remains to fully elucidate the cellular and molecular mechanisms underlying the formation and maintenance of the abnormal vessels.

Updates in Genetic Testing for Head and Neck Vascular Anomalies

Vascular anomalies include benign or malignant tumors or benign malformations of the arteries, veins, capillaries, or lymphatic vasculature. The genetic etiology of the lesion is essential to define the lesion and can help navigate choice of therapy. . In the United States, about 1.2% of the population has a vascular anomaly, which may be underestimating the true prevalence as genetic testing for these conditions continues to evolve.

Work-Up and Treatment Strategies for Individuals with PIK3CA-Related Disorders: A Consensus of Experts from the Scientific Committee of the Italian Macrodactyly and PROS Association

PIK3CA-related disorders encompass many rare and ultra-rare conditions caused by somatic genetic variants that hyperactivate the PI3K-AKT-mTOR signaling pathway, which is essential for cell cycle control. PIK3CA-related disorders include PIK3CA-related overgrowth spectrum (PROS), PIK3CA-related vascular malformations and PIK3CA-related non-vascular lesions. Phenotypes are extremely heterogeneous and overlapping. Therefore, diagnosis and management frequently involve various health specialists. Given the rarity of these disorders and the limited number of centers offering optimal care, the Scientific Committee of the Italian Macrodactyly and PROS Association has proposed a revision of the most recent recommendations for the diagnosis, molecular testing, clinical management, follow-up, and treatment strategies. These recommendations give insight on molecular diagnosis, eligible samples, preferable sequencing, and validation methods and management of negative results. The purpose of this paper is to promote collaboration between health care centers and clinicians with a joint shared approach. Finally, we suggest the direction of present and future research studies, including new systemic target therapies, which are currently under evaluation in several clinical trials, such as specific inhibitors that can be employed to downregulate the signaling pathway.

Mosaic pathogenic variants in AKT3 cause capillary malformation and undergrowth

Capillary malformations are slow-flow vascular malformations that affect the microcirculation including capillaries and post capillary venules and can be associated with growth differences. Specifically, the association of capillary malformations with undergrowth is a vastly understudied vascular syndrome with few reports of genetic causes including PIK3CA, GNAQ, and GNA11. Recently, a somatic pathogenic variant in AKT3 was identified in one child with a cutaneous vascular syndrome similar to cutis marmorata telangiectatica congenita, undergrowth, and no neurodevelopmental features. Here, we present a male patient with a capillary malformation and undergrowth due to a somatic pathogenic variant in AKT3 to confirm this association. It is essential to consider that mosaic pathogenic variants in AKT3 can cause a wide spectrum of disease. There is a need for future studies focusing on capillary malformations with undergrowth to understand the underlying mechanism.

Undergrowth Of First Toe In PiK3CA-Related Overgrowth Spectrum (PROS)

BACKGROUND

PIK3CA-related overgrowth syndrome (PROS) include a heterogeneous group of disorders characterized by segmental overgrowth secondary to somatic mosaic activating variants in PIK3CA. Segmental undergrowth is more uncommon and has been less studied but pathogenic variants in PIK3CA have also been found. With this in mind, we have noticed a group of patients with PROS that present an undergrowth component associated with their focal overgrowth.

METHODS

Retrospective review of patients with PROS presenting overgrowth of the lower limb and undergrowth of the ipsilateral first toe was performed.

RESULTS

Six patients were included, 4 female and 2 male with a median age of 16.8 years. All patients presented a PROS phenotype with overgrowth of the lower limb and undergrowth of ipsilateral first toe. A PIK3CA pathogenic variant was confirmed in all patients. Patients underwent multiple treatments, currently all are receiving alpelisib with a mean duration of 15.8 months (1-39) and partial response in lipomatosis and vascular anomalies but no response in overgrowth and undergrowth so far.

CONCLUSIONS

Pathogenic variants in the same gene can create different phenotypes depending on the time and place of the mutation. There is little information regarding opposing phenotpyes in the same patient with PROS. The presence of undergrowth in our series might be explained by genetic, embryogenic, maternal, or placental factors but needs to be further investigated.

Updates on Sturge-Weber Syndrome

Sturge-Weber syndrome (SWS) is a rare, noninherited neurovascular disorder characterized by abnormal vasculature in the brain, skin, and eye. Patients with SWS characteristically have facial capillary malformation, also known as port-wine birthmark, a leptomeningeal vascular malformation seen on contrast-enhanced magnetic resonance imaging images, abnormal blood vessels in the eye, and glaucoma. Patients with SWS have impaired perfusion to the brain and are at high risk of venous stroke and stroke-like episodes, seizures, and both motor and cognitive difficulties. While the activating R183Q GNAQ somatic mutation is the most common somatic mutation underlying SWS, recent research also implicates that GNA11 and GNB2 somatic mutations are related to SWS. Recent retrospective studies suggest the use of low-dose aspirin and vitamin D in treatment for SWS and prospective drug trials have supported the usefulness of cannabidiol and Sirolimus. Presymptomatic treatment with low-dose aspirin and antiepileptic drugs shows promising results in delaying seizure onset in some patients. This review focuses on the latest progress in the field of research for Sturge-Weber syndrome and highlights directions for future research.