Cerebrofacial vascular metameric syndrome is caused by somatic pathogenic variants in PIK3CA

Abstract

Disorganized morphogenesis of arteries, veins, capillaries, and lymphatic vessels results in vascular malformations. Most individuals with isolated vascular malformations have postzygotic (mosaic), activating pathogenic variants in a handful of oncogenes within the PI3K–RAS–MAPK pathway (Padia et al., Laryngoscope Investig Otolaryngol 4: 170–173 [2019]). Activating pathogenic variants in the gene PIK3CA, which encodes for the catalytic subunit of phosphatidylinositol 3-kinase, are present in both lymphatic and venous malformations as well as arteriovenous malformations in other complex disorders such as CLOVES syndrome (congenital, lipomatous, overgrowth, vascular malformations, epidermal anevi, scoliosis) (Luks et al., Pediatr Dev Pathol 16: 51 [2013]; Luks et al., J Pediatr 166: 1048–1054.e1–5 [2015]; Al-Olabi et al., J Clin Invest 128: 1496–1508 [2018]). These vascular malformations are part of the PIK3CA-related overgrowth spectrum, a spectrum of entities that have regionalized disordered growth due to the presence of tissue-restricted postzygotic PIK3CA pathogenic variants (Keppler-Noreuil et al., Am J Med Genet A 167A: 287–295 [2015]). Cerebrofacial vascular metameric syndrome (CVMS; also described as cerebrofacial arteriovenous metameric syndrome, Bonnet–Dechaume–Blanc syndrome, and Wyburn–Mason syndrome) is the association of retinal, facial, and cerebral vascular malformations (Bhattacharya et al., Interv Neuroradiol 7: 5–17 [2001]; Krings et al., Neuroimaging Clin N Am 17: 245–258 [2007]). The segmental distribution, the presence of tissue overgrowth, and the absence of familial recurrence are all consistent with CVMS being caused by a postzygotic mutation, which has been hypothesized by previous authors (Brinjiki et al., Am J Neuroradiol 39: 2103–2107 [2018]). However, the genetic cause of CVMS has not yet been described. Here, we present three individuals with CVMS and mosaic activating pathogenic variants within the gene PIK3CA. We propose that CVMS be recognized as part of the PIK3CA-related overgrowth spectrum, providing justification for future trials using pharmacologic PIK3CA inhibitors (e.g., alpelisib) for these difficult-to-treat patients.

Cerebrofacial venous metameric syndrome type 2+3: face is the index of brain

“…Due to the segmental distribution of the neural crest and mesoderm, the neural crest cells and the mesoderm at any segmental level occupy the same facial vascular territory, thus explaining the metameric nature of vascular malformations [8] . With the advances in research in the field of genetics, many genetic pathways involved in the development of vascular malformation have been unearthed, with multiple genes such as GNAQ, mTOR, PI3K, etc., which ultimately regulate the transcription of the growth factors, and mutations in one or more of these genes may result in specific venous metameric syndromes [3 , 9] .…”

Cerebrofacial venous metameric syndrome (CVMS) type I: constellation of imaging and clinical findings

“…2 The abnormality is thought to be caused by somatic mutations occurring prior to the migration of neural crest cells, which can lead to various venous abnormalities along the facial, osseous and cerebral planes which follow a segmental or 'metameric' distribution. 3 CVMS is classified into three groups: medial prosencephalic (olfactory) which involve the forehead, nose, corpus callosum, hypothalamus and hypophysis (CVMS 1); lateral prosencephalic (optic) which involve the temporo-parietaloccipital lobes, retina, optic nerve, eye, thalamus, maxilla and cheek (CVMS 2) and rhombencephalic/mesencephalon (otic) which affect the cerebellum, brainstem, lower face, mandible, petrous bone, and maxilla (CVMS 3). 4…”

“…The abnormality is thought to be caused by somatic mutations occurring prior to the migration of neural crest cells, which can lead to various venous abnormalities along the facial, osseous and cerebral planes which follow a segmental or ‘metameric’ distribution 3…”

Cerebrofacial arteriovenous metameric syndrome type I + II + III: An unusual case

“…Cerebrofacial arteriovenous metameric syndrome (CAMS), also recognized as cerebrofacial vascular metameric syndrome, Wyburn–Mason Syndrome, and Bonnet–Dechaume–Blanc Syndrome, represents a complex disorder characterized by metameric distribution involving retinal, facial, cerebral, and cerebellar vascular malformations. 1 It is classified into three subgroups based on prosencephalon or rhombencephalon involvement. CAMS I encompasses the medial prosencephalic group involving the hypothalamus, pituitary, and nasal regions.…”