Imperial College London

Claire L. Shovlin PhD FRCP

Faculty of MedicineNational Heart & Lung Institute

Professor of Practice (Clinical and Molecular Medicine)



c.shovlin Website




534Block L Hammersmith HospitalHammersmith Campus





Basic clinical information and our clinically-focussed Research Newletters are provided below.   

HHT (hereditary haemorrhagic telangiectasia) is a heritable disorder that affects approximately 1 in 5,000 individuals. At present in the UK, most people with HHT are not diagnosed, though many will be aware that they, or family members, have frequent nosebleeds. HHT leads to the development of abnormal blood vessels. When present in the nose, and in the gut, they may bleed. For people with recurrent bleeds, over long periods, chronic bleeding exhausts the body’s iron stores, and they may become anaemic. HHT also leads to the development of abnormal vessels called arteriovenous malformations (AVMs) in internal organs such as the lungs, liver and brain, and can lead to other rare complications. Most people with HHT are well, working, and exercising. In addition, our latest genetic data shows that HHT may be virtually undetectable clinically, even in families where someone else is more severely affected.  However mildly or severely affected the person is in terms of bleeding and anaemia, HHT screening and “wise HHT Public Health” is important to limit complications in later life, alongside education of general health care practitioners so that they can deliver usual healthcare, as required through life.

  • STOP PRESS: Click here for the 2022 VASCERN Framework manuscript for Management of HHT in General and Speciality Care
  • STOP PRESS: Click here for our 2022 HHT Information Sheet

Pulmonary arteriovenous malformations (PAVMs) affect 50% of people with HHT, and also occur in people without HHT. To understand PAVMs, it is helpful to think how the heart pumps blood around the body.  When the blood returns to the heart, before it goes round the body a second time, it is sent to the lungs to pick up oxygen. Critically, at the same time, waste is removed in a similar way to how a strainer mesh operates in a kitchen sink.  If PAVMs are present, it is like having a second plug hole in the sink, this time without the strainer mesh.  In the circulation, PAVMs provide a fast bypass, and any blood passing through these vessels goes straight back to the heart.  This means blood is not processed properly leading to low oxygen levels (which are tolerated very well), and other changes in arterial blood.  As for HHT, most people with PAVMs are well, working and exercising.  Again though, there are very important steps people with PAVMs can take to improve their health, particularly regarding embolization treatments, pregnancy and dental care.

  • STOP PRESS: Click here for the 2022 VASCERN Frameworks for management of PAVMs in general and speciality care
  • STOP PRESS: Click here for the 2022 Neurology Review of PAVMs targeting Neurological care for stroke and stroke prevention

2022 Summary information from our group is available in the following research and clinical support items. Earlier research newsletters covering additional topics were updated for 2021 where the topics were not fully covered in later newsletters.  The key publications from this period are available here . 

· 2022 HHT Information Sheet  
-What HHT is, how we recognise HHT, and what we do if HHT is present
-How your local doctors can know what to do when you see them
-Brief introduction to the NHS Rare Disease Collaborative Network (RDCN) for HHT

· 2020 PAVM and HHT Research Newsletter   
- PAVMs: MRI scans post embolisation; breathlessness, antibiotics; COVID
- HHT: severe anemia; blood thinners; COVID; VASCERN HHT links

· 2019 HHT Research Newsletter
- Introduction to VASCERN HHT, the European Reference Network dedicated to HHT chaired by Shovlin 2016- Brexit Dec 2020; cancer rates and HHT

· The Oxygen Train  
- An evidence based- model for the circulation, anemia and low oxygen levels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

· 2017 Research Newsletter ( 2021 update) 
- HHT and blood thinners; HHT nosebleeds; health benefits from HHT

· 2016 HHT Iron Research Newsletter (2021 update)
- Getting the iron balance right: Understanding requirements and sources, and risks of too little and too much iron

· 2015 HHT and PAVM Research Newsletter (2021 update)
- Anaemia; other effects of low iron levels; low oxygen levels; exercise

· 2012 HHT Research Newsletter (2021 update) 
- Blood clots; blood clots and low iron levels; flying

· 2011 PAVM and HHT Research Newsletter (2021 update)
- Why PAVMs are important; HHT clinical diagnosis; pregnancy