Autosomal dominant hereditary benign telangiectasia maps to the CMC1 locus for capillary malformation on chromosome 5q14

Inherited neurovascular diseases affecting cerebral blood vessels and smooth muscle

Neurovascular diseases are among the leading causes of mortality and permanent disability due to stroke, aneurysm, and other cardiovascular complications. Cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) and Marfan syndrome are two neurovascular disorders that affect smooth muscle cells through accumulation of granule and osmiophilic materials and defective elastic fiber formations respectively. Moyamoya disease, hereditary hemorrhagic telangiectasia (HHT), microcephalic osteodysplastic primordial dwarfism type II (MOPD II), and Fabry's disease are disorders that affect the endothelium cells of blood vessels through occlusion or abnormal development. While much research has been done on mapping out mutations in these diseases, the exact mechanisms are still largely unknown. This paper briefly introduces the pathogenesis, genetics, clinical symptoms, and current methods of treatment of the diseases in the hope that it can help us better understand the mechanism of these diseases and work on ways to develop better diagnosis and treatment.

Genetics of hemangiomas, vascular malformations, and primary lymphedema

With improved genetic testing and genomic sequencing, abnormalities are increasingly being identified in affected or germline tissues in DNA of patients with vascular tumors, vascular malformations, and lymphedema. Recognition of the genetics of vascular anomalies should help clinicians make more specific diagnoses, anticipate diagnosis-specific morbidities, provide better genetic counseling, and have a better understanding of the pathogenesis of these anomalies. Growing pharmacologic options, including therapies targeted to specific mutations, with obvious parallels to cancer treatment now allow the pediatric hematologist-oncologist to assume a more prominent role in clinical care and research for patients with these diagnoses. We summarize genes and genetic loci that have been associated with vascular anomalies and offer guidelines for patient evaluations.

RASA1 mutations and associated phenotypes in 68 families with capillary malformation-arteriovenous malformation

Capillary malformation-arteriovenous malformation (CM-AVM) is an autosomal-dominant disorder, caused by heterozygous RASA1 mutations, and manifesting multifocal CMs and high risk for fast-flow lesions. A limited number of patients have been reported, raising the question of the phenotypic borders. We identified new patients with a clinical diagnosis of CM-AVM, and patients with overlapping phenotypes. RASA1 was screened in 261 index patients with: CM-AVM (n = 100), common CM(s) (port-wine stain; n = 100), Sturge-Weber syndrome (n = 37), or isolated AVM(s) (n = 24). Fifty-eight distinct RASA1 mutations (43 novel) were identified in 68 index patients with CM-AVM and none in patients with other phenotypes. A novel clinical feature was identified: cutaneous zones of numerous small white pale halos with a central red spot. An additional question addressed in this study was the "second-hit" hypothesis as a pathophysiological mechanism for CM-AVM. One tissue from a patient with a germline RASA1 mutation was available. The analysis of the tissue showed loss of the wild-type RASA1 allele. In conclusion, mutations in RASA1 underscore the specific CM-AVM phenotype and the clinical diagnosis is based on identifying the characteristic CMs. The high incidence of fast-flow lesions warrants careful clinical and radiologic examination, and regular follow-up.

Parkes Weber syndrome, vein of Galen aneurysmal malformation, and other fast-flow vascular anomalies are caused by RASA1 mutations

Capillary malformation-arteriovenous malformation (CM-AVM) is a newly recognized autosomal dominant disorder, caused by mutations in the RASA1 gene in six families. Here we report 42 novel RASA1 mutations and the associated phenotype in 44 families. The penetrance and de novo occurrence were high. All affected individuals presented multifocal capillary malformations (CMs), which represent the hallmark of the disorder. Importantly, one-third had fast-flow vascular lesions. Among them, we observed severe intracranial AVMs, including vein of Galen aneurysmal malformation, which were symptomatic at birth or during infancy, extracranial AVM of the face and extremities, and Parkes Weber syndrome (PKWS), previously considered sporadic and nongenetic. These fast-flow lesions can be differed from the other two genetic AVMs seen in hereditary hemorrhagic telangiectasia (HHT) and in phosphatase and tensin homolog (PTEN) hamartomatous tumor syndrome. Finally, some CM-AVM patients had neural tumors reminiscent of neurofibromatosis type 1 or 2. This is the first extensive study on the phenotypes associated with RASA1 mutations, and unravels their wide heterogeneity.

Evidence for clinical and genetic heterogeneity in hereditary benign telangiectasia

BACKGROUND

Telangiectases are abnormal dilatations of end vessels in the subpapillary plexus of the papillary dermis. Hereditary benign telangiectasia (HBT) (OMIM 187260) is a genetic skin disorder, characterized by multiple cutaneous telangiectases appearing in the first years of life in various locations. Several familial cases of HBT have been described displaying autosomal dominant inheritance. In some of the described pedigrees, telangiectases are limited to sun-exposed areas, whereas in others lesions are randomly distributed over the body. The disorder has been previously mapped to a 7Mb interval on chromosome 5q14 (CMC1 locus) in an Italian pedigree with randomly distributed telangiectases.

OBJECTIVES

A large pedigree of HBT with photodistributed lesions is described. We sought to determine whether photodistributed HBT is linked to the CMC1 locus.

METHODS

In all, 35 family members were examined. DNA was extracted from blood and saliva samples. Linkage analysis to CMC1 locus on chromosome 5q14 was screened by using 3 polymorphic markers.

RESULTS

In all, 23 family members were found to have variable numbers of cutaneous radiating macular telangiectases, measuring 1 to 3 cm and distributed over the face, back of the hands, and forearms. HBT in this family is inherited in an autosomal dominant pattern with incomplete penetrance. Linkage to the CMC1 locus was excluded.

LIMITATION

Only one family, although very large, was studied in this project.

CONCLUSIONS

Clinical and genetic heterogeneity is evident in HBT. Photodistributed HBT is not related pathogenically to capillary malformations or to randomly distributed hereditary telangiectases and should be recognized as a separate entity.

Hereditary benign telangiectasia: first case in Iran

A 14-year-old boy was referred to the Dermatology Clinic of the Medical University of Mashhad, Iran, with numerous cutaneous telangiectasias on the face, ears, lips, and back of the hands, with lesions in the temporal region being the first to appear (Figs 1-3). His mother stated that the lesions had been present for 10 years with an increase in the past 6 months. He had no history of bleeding from the nose, mouth, gastrointestinal tract, and other mucosal surfaces, and there was no sign of organ involvement. On inspection, no lesions were detected on the nasal mucosa, external ear, over the tympanic membrane, or mouth. The patient is one member of a family of six. His mother is healthy, but similar lesions were seen in his father, sister and one of his brothers with similar distributions. Lesions were also seen in his aunt and paternal grandmother, showing disease distribution in six members of this family from three generations. The oldest brother is 20 years of age and mentioned the onset of disease from the age of 10 years. The sister is 18 years of age and lesions started to appear 7 years ago; she claims that the lesions regress during her menstrual period. The youngest brother is 4 years of age and shows no sign of cutaneous lesions as yet. The parents are not consanguineous. Generalized telangiectasia with a predominant distribution on light-exposed skin, an autosomal dominant inheritance, and no sign of systemic or mucosal involvement and bleeding disorders indicates a diagnosis of hereditary benign telangiectasia. Our patient did not consent to biopsy.

External cervical root resorption involving multiple maxillary teeth in a patient with hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an inherited syndrome characterized by mucocutaneous telangiectases that commonly involve the tongue, lips, fingers, and conjunctiva. While root resorption has been reported in association with central hemangiomas of bone, the association of HHT with external cervical root resorption has not been described to date. We report a case of a 57-year-old female with HTT who presented with advanced cervical root resorption involving multiple maxillary anterior teeth. Histologic examination of the gingival tissue adjacent to the area of root resorption demonstrated multiple thin-walled vascular elements as well as larger vascular channels surrounded by a thickened muscular layer. We hypothesize that the external root resorption seen in this case is the result of the HHT-related vascular process in the adjacent gingival tissue.

RASA1: variable phenotype with capillary and arteriovenous malformations

Capillary malformation-arteriovenous malformation (CM-AVM) is a newly discovered hereditary disorder. Its defining features are atypical cutaneous multifocal capillary malformations often in association with high-flow lesions: cutaneous, subcutaneous, intramuscular, intraosseous and cerebral arteriovenous malformations and arteriovenous fistulas. Some patients have Parkes Weber syndrome - a large congenital cutaneous vascular stain in an extremity, with bony and soft tissue hypertrophy and microscopic arteriovenous shunting. In the past, arteriovenous malformations and arteriovenous fistulas had been considered non-hereditary. A classical genetic approach was used to identify the locus. Candidate gene screening pinpointed mutations in RASA1 (p120-RASGAP) - a RasGTPase. RASA1 reverts active GTP-bound Ras into inactive GDP-bound form. Murine Rasa1 knockout and tetraploid-aggregated embryos with RNA interference exhibited abnormal vascular development. Lack of RASA1 activity caused inhibition of cell motility, possibly through p190-RhoGAP. Thus, RASA1 defects probably cause abnormal angiogenic remodeling of the primary capillary plexus that cannot be compensated for by other RasGAPs: RASA2, RASAL and NF1. Signaling pathways involving RASA1 might offer novel targets for treatment of high-flow vascular anomalies.

[Capillary malformations associated with cerebral cavernous malformation]

INTRODUCTION

Capillary malformations such as benign hereditary telangiectasia are a familial affection, of dominant autosomal transmission, characterized by the progressive development of cutaneous telangiectasia during childhood. The association with cutaneous vascular, arteriovenous or lymphatic malformations is exceptional and has only recently been described.

CASE REPORT

A 5 year-old girl presented with widespread erythematous, predominantly telangiectasic, congenital and acquired macules when she was one year-old. Her history was marked by right temporal cerebral hemorrhage at the age of 4, revealing a right temporal cavernoma-like vascular malformation. The familial history of telangiectasic macules and clinical and histological examination led to the diagnosis of benign hereditary telangiectasia.

DISCUSSION

This case report raises doubt on the exclusively cutaneous nature of benign hereditary telangiectasic-type capillary malformations. Moreover, it illustrates the possibility of a particular clinical form of this affection, associating classical telangiectasia and post-wine stain-type macules. The recent localization of the locus implied in this affection in 5q14 in the same chromosomic space as the CMC1 locus incriminated in familial capillary malformations, suggests that these two affections are in fact phenotype variations of a single and same clinical entity.