What Is Hereditary Haemorrhagic Telangiectasia?

Have you ever felt like there is something not completely right with your overall health? Are you experiencing recurrent nosebleeds, or spider veins appearing under the skin indicated by red or purple spots? Do you happen to know if you have a family history of hereditary haemorrhagic telangiectasia (HHT)? 

HHT is an inherited condition that results in the altered formation of blood vessels. Another well-known name for HHT is Osler-Weber-Rendu syndrome, named after the clinicians who characterised the condition. It is thought to be an inherited condition linked to certain genetic mutations.

It is identified by the appearance of telangiectasias and arteriovenous malformations (AVM) in multiple organs and is usually diagnosed using the Curacao criteria. There is no cure. However, treatment for symptom management is available.

Overview

Hereditary haemorrhagic telangiectasia (HTT) is an autosomal dominant hereditary disorder, meaning only one parent must have a genetic mutation for the child to develop the condition.¹ This vascular (blood vessel-related) disorder can result in excessive bleeding due to the faulty formation of the blood vessels. There are different diagnostic methods and symptoms, as well as management and treatment options, depending on the severity of the syndrome and the location where the blood vessels are affected. Moreover, as a result, many complications can occur that can have a further toll on the patient's general health.

Causes of hereditary haemorrhagic telangiectasia

Osler-Weber-Rendu syndrome is thought to be an autosomal dominant disorder that is the result of mutations in specific genes, the most common ones being endoglin, ACVRL1/ALK1 and in rare cases SMAD4.² Also direct, first-degree relative family history presents a higher incidence rate of HTT development.

Signs and symptoms of hereditary haemorrhagic telangiectasia

Patients can be symptomatic or asymptomatic. The major signs of HHT are:

• Telangiectasia: small, widened blood vessels on the skin
• Arteriovenous/vascular malformations (AVMs): when an artery and a vein form a connection/tangle disrupting correct blood flow and oxygen supply

Telangiectases are usually found in the following: 

• oral cavity (mouth)
• Lips
• Fingers
• Upper gastrointestinal (GI) tract
• The internal part of the nose (nasal mucosa). 

AVMs on the other site, usually occur in major organs such as the: 

• Lungs
• Liver
• Brain (spinal AVMs, brain vascular malformations, liver vascular malformations)
• Nose bleeds (epistaxis): due to telangiectases located at the internal side of the nose (>95% of patients)
• Bleeding: gastrointestinal (GI tract); intracranial (inside the skull); pulmonary (inside the lungs)

Brain/cerebral vascular malformations are observed in 10-23% of HHT patients; gastrointestinal vascular malformations in around 70%; hepatic/liver vascular malformations (HAVMs) in up to 70% of patients diagnosed with HHT.³ Around half of HHT patients present with epistaxis (nosebleeds) by the age of 10 and 80-90% by the age of 21. The extent of the nosebleeds varies between mild epistaxis - 3 to 6 times per year for a time duration of less than one minute to more severe epistaxis characterised by multiple nosebleeds per day.⁴

Management and treatment for HHT

Although there is no cure for HHT, there are treatment options available for the management of symptoms, prevention of further disease progression and treatment of complications.⁵ There are surgical, conventional, and drug intervention procedures that can be applied to HHT patients:

• Epistaxis (nosebleeds): Tamoxifen, haemostatic agents, tranexamic acid, and  propranolol medication⁶
• Epistaxis: bipolar cautery (the use of electricity to seal off blood vessels), or laser photocoagulation (a laser used to burn defective blood vessels, stopping bleeding)
• GI tract bleeding: blood transfusions and antiangiogenic agents⁷
• Anaemia: iron replacement therapy (reduced quantity of blood iron due to continuous blood loss)
• Liver AVMs: liver transplantation (in most serious cases) or medication
• Brain AVMs: surgery, stereotactic radiosurgery, embolotherapy

Intake of anticoagulants e.g. warfarin, and nonsteroidal anti-inflammatory agents (NSAIDs) e.g. aspirin, should be avoided.⁸ Certain lifestyle activities are also not recommended such as scuba diving.

Diagnosis

There are several methods used for the clinical diagnosis of HHT:⁹

• Curacao criteria
• Family history: check for first-degree relatives with the condition (e.g. parents)
• Molecular diagnosis: screening for mutations present in the ACVRL1, SMAD4, and endoglin genes (around 90% of the patients)
• Screening for AVMs: Using MRI (Magnetic Resonance Imaging) and CT (Computed tomography)
• Genetic analysis
• Physical examination: checking for telangiectasia (red/purple spots) on body regions such as the fingers, lips, tongue, pharynx, cheeks, and/or conjunctiva (inner lining of the eyelids). Liver checks for normal function should also be performed
• Full blood count (FBC) and serum ferritin (the amount of iron storage in body tissues)

The Curacao criteria were created in 1999 specifically for HHT diagnosis and consist of four indicators:

• Dilated capillaries (telangiectasia) in the skin and mucous (inner lining of organs and body cavities) membranes
• Recurrent spontaneous nosebleeds
• Arteriovenous/vascular malformations (AVMs)
• Positive family history

If less than two out of the four statements are met, a HHT diagnosis is unlikely. If two out of the four criteria are met, a HHT diagnosis is suspected. If three out of the four criteria are met, a Hereditary hemorrhagic telangiectasia diagnosis can be established. Molecular diagnosis is usually done for detection of asymptomatic patients to prevent future complications.

FAQs

How can I prevent HHT?

HHT cannot be prevented. However, if you know of any direct medical history of HHT in your family, you should inform your doctor. That might enable you to catch the condition in time and avoid any future complications.

How common is HHT?

HHT affects roughly 1-2 in 100,000 babies, but depending on the geographic region it has been recorded to reach up to 1 in 3,500 to 5000.

Who is at risk of HHT?

People with a family history of HHT have a higher chance of developing the disease. Also, people with genetic mutations in certain genes such as the endoglin or SMAD4 gene are at an increased risk of HHT.

When should I see a doctor?

If you experience any abnormal symptoms, frequent nosebleeds, and/or know you have a family history of HHT you should pay a visit to your GP.

Summary

Hereditary haemorrhagic telangiectasia (HHT) is a rare condition, considered to be caused by an autosomal dominant mutation. Abnormalities/mutations in specific genes and a direct family history of the condition lead to a higher incidence of HHT. The condition is also known as Osler-Weber-Rendu syndrome and it is not very common, affecting approximately 1-2 in 100,000 babies. However, this varies depending on the geographic region. The most common symptoms are nosebleeds and potentially AVMs (liver, brain, pulmonary, and vascular malformations). Although no cure has been developed as of yet, many medical interventions can improve symptom management and prevent further complications (e.g. anaemia). Such interventions include surgical procedures, the use of medication, and sometimes home remedies. If you or someone you know has been diagnosed with hereditary hemorrhagic telangiectasia, your clinician may have registered you at with The National Congenital Anomaly and Rare Disease Registration Service (NCARDRS). It will provide you with further guidance and information on what to do. It will also give the NHS more statistical data on the incidence of this condition, and improve healthcare services.