Facebook Pixel Code
Section banner image
Paediatric Laboratory Medicine

Hereditary Hemorrhagic Telangiectasia: ENG Sequencing

Clinical Significance

Hereditary hemorrhagic telangiectasia (HHT) results from the presence of multiple arteriovenous malformations (AVMs) in which intervening capillaries between arteries and veins are absent, resulting in direct connections between arteries and veins. Small AVMs or telangiectases near the skin surface and surface of oral and gastrointestinal (GI) mucosa membranes often rupture and bleed with minor trauma. Large AVMs often cause more severe symptoms when they occur in brain, lung, GI tract or more rarely liver and spine. Complications from bleeding or shunting may be sudden and catastrophic.

HHT is an autosomal dominant disorder which can be divided into two clinically indistinct forms based on the protein defect: HHT1 is caused by defects in the endoglin protein encoded by the ENG gene located on chromosome 9 at 9q34.1 while HHT2 is caused by defects in the serine/threonine receptor kinase R3 encoded by the ACVRL1 (ALK1) gene located on chromosome 12 at 12q11-q14. Approximately 80-90% of all mutations causing HHT1 or HHT2 are point mutations or small insertions/deletions. Deletions in the ENG gene may also cause up to 10% of HHT.

HHT is present when an individual has one copy of the defective gene (ENG or ACVRL1). Silent carriers may not be affected themselves by HHT, however, they may transmit the defective gene to their offspring. There is a 50% chance that their baby will have the gene for HHT and thus may develop symptoms at some stage in their life. There is a 50% chance that the baby will not have HHT.

Test Name

Hereditary Hemorrhagic Telangiectasia: ENG Sequencing

Alternate Name/ Synonym

  • HHT, Osler-Weber-Rendu Disease

Gene Name

  • ENG

Alternate Gene Name

HHT1

Test Code

HHT

Division

Molecular Genetics

Method

Sequencing

External Proficiency Testing

CAP

Turn Around Time

2 weeks (Prenatal samples), 2-3 weeks (Pregnancy/Urgent samples), 4-6 weeks (Routine)

Protein

Endoglin

Disease/Condition

Hereditary Hemorrhagic Telangiectasia

Specimen Type

Blood; extracted DNA is not accepted for ENG and ACVRL1 Deletion/Duplication Analysis

If sending a prenatal sample, please contact the laboratory prior to sending sample to discuss sample requirements.

For details about specimen requirements, please refer to: Specimen Type & Requirements (PDF).

Minimum Specimen Requirements

5-10 mL EDTA or ACD 0.5 mL EDTA (neonate); minimum 10 ug in 100 uL low TE (pH8.0)

Storage/Transportation

Room Temperature

Special Requirements

Special Instructions for Genome Diagnostics Samples

If sample shipment >48 hours, ship on ice.

Approval is not required

CPT Codes

81479

Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Canada
Phone: 416-813-7200
Phone: 1-855-381-3212

Interpretation

Interpretation is provided in report