Hereditary Hemorrhagic Telangiectasia

Hereditary Hemorrhagic Telangiectasia (HHT) Panel, Sequencing and Deletion/Duplication 2009337
Method: Massively Parallel Sequencing/Exonic Oligonucleotide-based CGH Microarray

Recommended test for symptomatic individuals who do not meet clinical criteria for HHT

Hereditary Hemorrhagic Telangiectasia (ACVRL1 and ENG) Sequencing and Deletion/Duplication 0051382
Method: Polymerase Chain Reaction/Sequencing/Multiplex Ligation-dependent Probe Amplification

Recommended test for symptomatic individuals who meet clinical criteria for HHT

Recommended test for symptomatic individuals who meet clinical criteria for HHT

Familial Mutation, Targeted Sequencing 2001961
Method: Polymerase Chain Reaction/Sequencing
  • Recommended test for a known familial sequence variant previously identified in a family member.
  • A copy of the family member’s test results documenting the known familial variant is required.

Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation in the skin, mucous membranes, and often in organs such as the lungs, liver, and brain. Genetic testing can confirm a diagnosis.

Disease Overview


  • Spontaneous and recurring nosebleeds
  • Cutaneous and/or mucosal telangiectases, predominantly on the face, lips, hands, and in oral, nasal, and gastrointestinal mucosa
  • Arteriovenous malformations (AVMs) affecting the lungs, liver, and brain
  • HHT symptoms and juvenile polyps are present with juvenile polyposis  syndrome (JPS)/HHT (SMAD4)


  • Approximately 95% of individuals will develop nosebleeds or telangiectases.
  • Penetrance is age dependent.




Autosomal dominant

Test Description

See the Genes Tested table for the coding regions and intron-exon boundaries of six genes, the 5' untranslated region of ENG, and a region of ACVRL1 intron 9 encompassing the CT-rich variant hotspot region.

Clinical sensitivity

  • 87% of individuals meeting consensus clinical diagnostic criteria for HHT will have a causative variant in one of the genes tested.
    • Variable for those with symptoms but who do not meet diagnostic criteria
  • ACVRL1 and ENG are causative for ~85% of HHT.    
    • 75% detectable by sequencing
    • 10% detectable by large deletion/duplication analysis
  • SMAD4 is causative for 1-3% of HHT 
  • BMP9/GDF2 mutation are detected in <1% of individuals with no other causative variants. 
  • The clinical sensitivity for EPHB4 is unknown.


  • A negative result does not exclude a diagnosis of HHT or overlapping disorders.
  • Diagnostic errors can occur due to rare sequence variations.
  • Interpretation of this test result may be impacted if the individual has had an allogeneic stem cell transplantation.
  • The following will not be evaluated:
    • Variants outside the coding regions and intron-exon boundaries of the targeted genes
    • Regulatory region variants and deep intronic variants
    • Breakpoints of large deletions/duplications
    • Deletions/duplications in EPHB4
  • The following may not be detected:
    • Deletions/duplications/insertions of any size by massively parallel sequencing
    • Deletions/duplications less than 1kb in the targeted genes by array
    • Some variants due to technical limitations in the presence of pseudogenes, repetitive, or homologous regions
    • Low-level somatic variants

Analytical Sensitivity

For massively parallel sequencing:

Variant Class Analytical Sensitivity (PPA) Estimatea (%) Analytical Sensitivity (PPA) 95% Credibility Regiona (%)




Deletions 1-10 bp



Deletions 11-44 bp



Insertions 1-10 bp



Insertions 11-23 bp



aGenes included on this test are a subset of a larger methods-based validation from which the PPA values are derived.

bp, base pairs; PPA, positive percent agreement; SNVs, single nucleotide variants

Genes Tested

Gene Alias Symbol(s) MIM Number Disorder




HHT, type 2




HHT, type 1


HTK, Tyro11






HHT, type 5


RASA, GAP, CM-AVM, p120GAP, p120RASGAP, p120


CM-AVM, Parkes Weber syndrome





CM-AVM, capillary malformation-arteriovenous malformation

  1. Bossler AD, Richards J, George C, Godmilow L, Ganguly A. Novel mutations in ENG and ACVRL1 identified in a series of 200 individuals undergoing clinical genetic testing for hereditary hemorrhagic telangiectasia (HHT): correlation of genotype with phenotype. Hum Mutat. 2006; 27(7): 667-75. PubMed
  2. Gedge F, McDonald J, Phansalkar A, Chou L, Calderon F, Mao R, Lyon E, Bayrak-Toydemir P. Clinical and analytical sensitivities in hereditary hemorrhagic telangiectasia testing and a report of de novo mutations. J Mol Diagn. 2007; 9(2): 258-65. PubMed
  3. Prigoda NL, Savas S, Abdalla SA, Piovesan B, Rushlow D, Vandezande K, Zhang E, Ozcelik H, Gallie BL, Letarte M. Hereditary haemorrhagic telangiectasia: mutation detection, test sensitivity and novel mutations. J Med Genet. 2006; 43(9): 722-8. PubMed
  4. Richards-Yutz J, Grant K, Chao EC, Walther SE, Ganguly A. Update on molecular diagnosis of hereditary hemorrhagic telangiectasia. Hum Genet. 2010; 128(1): 61-77. PubMed
  5. Wooderchak-Donahue WL, McDonald J, O'Fallon B, Upton PD, Li W, Roman BL, Young S, Plant P, Fülöp GT, Langa C, Morrell NW, Botella LM, Bernabeu C, Stevenson DA, Runo JR, Bayrak-Toydemir P. BMP9 mutations cause a vascular-anomaly syndrome with phenotypic overlap with hereditary hemorrhagic telangiectasia. Am J Hum Genet. 2013; 93(3): 530-7. PubMed
  6. Amyere M, Revencu N, Helaers R, Pairet E, Baselga E, Cordisco M, Chung W, Dubois J, Lacour J, Martorell L, Mazereeuw-Hautier J, Pyeritz RE, Amor DJ, Bisdorff A, Blei F, Bombei H, Dompmartin A, Brooks D, Dupont J, González-Enseñat MA, Frieden I, Gérard M, Kvarnung M, Hanson-Kahn AK, Hudgins L, Léauté-Labrèze C, McCuaig C, Metry D, Parent P, Paul C, Petit F, Phan A, Quere I, Salhi A, Turner A, Vabres P, Vicente A, Wargon O, Watanabe S, Weibel L, Wilson A, Willing M, Mulliken JB, Boon LM, Vikkula M. Germline Loss-of-Function Mutations in EPHB4 Cause a Second Form of Capillary Malformation-Arteriovenous Malformation (CM-AVM2) Deregulating RAS-MAPK Signaling. Circulation. 2017; 136(11): 1037-1048. PubMed
  7. Faughnan ME, Palda VA, Garcia-Tsao G, Geisthoff UW, McDonald J, Proctor DD, Spears J, Brown DH, Buscarini E, Chesnutt MS, Cottin V, Ganguly A, Gossage JR, Guttmacher AE, Hyland RH, Kennedy SJ, Korzenik J, Mager JJ, Ozanne AP, Piccirillo JF, Picus D, Plauchu H, Porteous ME, Pyeritz RE, Ross DA, Sabba C, Swanson K, Terry P, Wallace MC, Westermann CJ, White RI, Young LH, Zarrabeitia R, HHT Foundation International - Guidelines Working Group. International guidelines for the diagnosis and management of hereditary haemorrhagic telangiectasia. J Med Genet. 2011; 48(2): 73-87. PubMed
  8. Marchuk DA, Guttmacher AE, Penner JA, Ganguly P. Report on the workshop on Hereditary Hemorrhagic Telangiectasia, July 10-11, 1997. Am J Med Genet. 1998; 76(3): 269-73. PubMed
  9. Porteous ME, Burn J, Proctor SJ. Hereditary haemorrhagic telangiectasia: a clinical analysis. J Med Genet. 1992; 29(8): 527-30. PubMed

Last Update: September 2019