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Hereditary haemorrhagic telangiectasia


Learning objectives

  • Learning
  • Understand
  • Integrate
  • Reflect

Introduction
  • Hereditary haemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu disease
  • Rare autosomal dominant genetic disorder that leads to abnormal blood vessel formation
  • Telangiectasia found in the skin, mucous membranes
  • Others found in the lungs, liver, and brain
  • Most Cerebral AVMs in the HHT population are symptomatic.
  • Family history of a parent, sibling or child with same
The prevalence of brain AVMs in HHT patients was 10.4% in a large analysis of trials with no significant difference between males and females
Aetiology
  • A disorder of angiogenesis with abnormal fragile blood vessels
  • Mutations in several genes, including the ACVRL1, ENG, and SMAD4 genes
  • HHT1 patients more likely to have brain AVMs than HHT2 patients.
Aetiology of stroke
  • Bleeding from a cerebral vascular malformations
  • Paradoxical embolism through a pulmonary AVM (rare)
  • The vessels lack contractile elements and so given direct arterial connection, bleeding from telangiectases can be brisk and difficult to stop. This may be seen with GI Bleeds.
Most individuals with a PAVM(s) have Hereditary haemorrhagic telangiectasia
Clinical
  • Difficulties with Epistaxis seen in most by adulthood
  • GI bleeding, Haematemesis, Melaena, Fe deficiency anaemia often over age of 50
  • Haemorrhagic stroke as risk of AVMS
  • Mucocutaenous lesions in skin and oral cavity and nose
  • Embolic stroke via paradoxical embolism via pulmonary AVM
  • Pulmonary AVM can rupture, leading to haemoptysis
Clinical Signs
Types
  • Type 1: mutations in the ENG gene. Brain AVMS in 13.4 %
  • Type 2: mutations in the ACVRL1 gene. Brain AVMS in 2.4 %
  • Juvenile polyposis/hereditary haemorrhagic telangiectasia syndrome is caused by mutations in the SMAD4 gene.
Differential
  • Vasculitis rash
  • Thrombocytopenia
  • Telangiectases of chronic liver disease are spider like with a central core and small vessels radiating outward
Diagnostic clinical criteria
Diagnostic clinical criteria
  1. Epistaxis (nosebleeds): spontaneous and recurrent.
  2. Mucocutaneous telangiectases: multiple, at characteristic sites (lips, oral cavity, fingers, and nose). Lesions are blanchable and usually punctuate, pink-red in color, and pinpoint to pinhead in size. Occasionally 2–5 mm macules, purple or “spidery.”
  3. Vascular
    • Visceral AVM.
    • Pulmonary
    • Cerebral
    • Hepatic
    • GI
    • Spinal
  4. Family history: a first-degree relative in whom HHT has been diagnosed using these criteria.

The clinical diagnosis of HHT is considered:

  • Definite when three or more findings are present;
  • Possible or suspected when two findings are present; and
  • Unlikely when fewer than two findings are present.

Note: These diagnostic criteria were established for adults and can be misleading when applied to children.

Investigations
  • FBC: exclude Fe deficiency anaemia from GI blood loss. ESR, CRP, U&E, LFTs
  • Brain Imaging - CT/MRI
  • CXR : may show lung lesion ? AVM
  • Angiography is AVM suspected. The Spetzler-Martin grade for HHT related lesions is 2 or less in nearly 90% of patients.
  • Bubble echo shown to be a sensitive screen for PAVMs and then CT Pulmonary angiogram if positive bubble echo. This avoids radiation in young adults. This may need repeated at 5 year intervals.
  • Colonoscopy and upper endoscopy +/- capsule endoscopy. Those with mutations in the SMAD4 gene may be at increased risk for polyps. Alternatively may be done to exclude other cause of Fe deficiency anaemia
  • Molecular genetic testing is used to establish the genetic subtype of hereditary haemorrhagic telangiectasia in a clinically affected individual and family, and for early diagnosis to allow for appropriate screening and preventive treatment.
Management
  • ABC, Stroke management, Acute management for GI Bleed as needed. Transfusion if needed.
  • ENT referral for epistaxis - Laser ablation is usually recommended as the intervention for control of mild to moderate nosebleeds
  • Gastroenterology review for GI bleeds. Iron replacement therapy for anaemia.
  • Avoid antithrombotic drugs. Antifibrinolytic drugs such as tranexamic acid have been used in select patients
  • Genetic counselling.
  • Management of Cerebral Arteriovenous Malformations if found. A recent study has found that functional outcomes were not statistically different between those who had surgery and those who didn't on long term follow-up. Link
  • Closure of Pulmonary AVM if embolic stroke by Interventional neuroradiology if needed.Any PAVM with a feeding artery > 1–3 mm detected by chest CT should be considered for treatment by transcatheter embolization.
References