The pathobiology of vascular malformations: insights from human and model organism genetics

Mosaic RAS/MAPK variants cause sporadic vascular malformations which respond to targeted therapy

BACKGROUND. Sporadic vascular malformations (VMs) are complex congenital anomalies of blood vessels that lead to stroke, life-threatening bleeds, disfigurement, overgrowth, and/or pain. Therapeutic options are severely limited, and multidisciplinary management remains challenging, particularly for high-flow arteriovenous malformations (AVM).

METHODS. To investigate the pathogenesis of sporadic intracranial and extracranial VMs in 160 children in which known genetic causes had been excluded, we sequenced DNA from affected tissue and optimized analysis for detection of low mutant allele frequency.

RESULTS. We discovered multiple mosaic-activating variants in 4 genes of the RAS/MAPK pathway, KRAS, NRAS, BRAF, and MAP2K1, a pathway commonly activated in cancer and responsible for the germline RAS-opathies. These variants were more frequent in high-flow than low-flow VMs. In vitro characterization and 2 transgenic zebrafish AVM models that recapitulated the human phenotype validated the pathogenesis of the mutant alleles. Importantly, treatment of AVM-BRAF mutant zebrafish with the BRAF inhibitor vemurafinib restored blood flow in AVM.

CONCLUSION. Our findings uncover a major cause of sporadic VMs of different clinical types and thereby offer the potential of personalized medical treatment by repurposing existing licensed cancer therapies.

FUNDING. This work was funded or supported by grants from the AVM Butterfly Charity, the Wellcome Trust (UK), the Medical Research Council (UK), the UK National Institute for Health Research, the L’Oreal-Melanoma Research Alliance, the European Research Council, and the National Human Genome Research Institute (US).

Nonepithelial Tumors and Tumor-like Lesions of the Skin and Subcutis in Children

This overview of mesenchymal tumors presenting in the skin and/or subcutis in children brings together the range of neoplasms and hamartomas which are seen in this age-group. It is not surprising from the perspective of the pediatric or general surgical pathologist that vascular anomalies, including true neoplasms and vascular malformations, are the common phenotypic category. Since there is considerable morphologic overlap among these lesions, clinicopathologic correlation may be more important than for many of the other mesenchymal tumors. The skin and subcutis are the most common sites of clinical presentation for the infantile myofibroma which is the most common of fibrous mesenchymal tumors in children. Several of the other mesenchymal tumors are more common adults-like dermatofibrosarcoma protuberans, but nonetheless have an important presence in children, even as a congenital neoplasm. A lipomatous tumor in a young child should be considered as a possible manifestation of an overgrowth syndrome.

Genetics meets pathology - an increasingly important relationship

The analytical power of modern methods for DNA analysis has outstripped our capability to interpret and understand the data generated. To make good use of this genomic data in a biomedical setting (whether for research or diagnosis), it is vital that we understand the mechanisms through which mutations affect biochemical pathways and physiological systems. This lies at the centre of what genetics is all about, and it is the reason why genetics and genomics should go hand in hand whenever possible. In this Annual Review Issue of The Journal of Pathology, we have assembled a collection of 16 expert reviews covering a wide range of topics. Through these, we illustrate the power of genetic analysis to improve our understanding of normal physiology and disease pathology, and thereby to think in rational ways about clinical management. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Pathophysiology, diagnosis, and management of glaucoma associated with Sturge-Weber syndrome

PURPOSE

Sturge-Weber syndrome (SWS), also known as encephalotrigeminal angiomatosis, is a condition which includes leptomeningeal hemangioma, facial angiomatosis or nevus flammeus, and ocular changes. SWS can lead to severe complications of anterior segment involving conjunctiva and eyelids, whereas posterior segment of the eye may also be affected by diffuse choroidal hemorrhages. This article was written with the objectives to determine the pathophysiology, diagnosis, and treatment of glaucoma associated with this rare and challenging disorder.

METHODS

A detailed literature search was conducted on PubMed, EMBASE, Cochrane Library, and Google Scholar using the key words. Forty-five articles matched our inclusion criteria that were included in this systematic review.

RESULTS

Glaucoma is the one of the commonest ocular manifestations of SWS. It is caused by anterior chamber malformations, increased pressure in the episcleral veins, and changes in ocular hemodynamics. Glaucoma associated with SWS is usually congenital but can develop adults as well. The treatment of glaucoma associated with SWS is quite challenging because of early-onset, severe visual field impairment at the time of diagnosis, and unresponsiveness to standard medical treatment. Several surgical procedures have been devised but the long-term control of the intraocular pressure and visual function remain unsatisfactory. Modifications in the filtration surgery techniques and use of newer anti-fibrotic agents have produced good control of intraocular pressure.

CONCLUSION

Management of glaucoma associated with SWS is multi-dimensional and needs both medical and surgical interventions for better control. The treatment should be devised on case to case basis depending upon the intraocular pressure, stage of the disease, and type of glaucoma.