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PNH in more detail?

This section gives additional information, looking in a little more detail at some aspects of PNH.

The defect that causes PNH occurs in a gene known as the PIG-A gene. This gene is present in the haemopoeitic stem cells (HSCs) of the bone marrow. These are cells which go on to form all of the cells in the blood. The PIG-A gene produces proteins known as the GPI-anchor, which are present on the surface of blood cells and attach protective proteins to the blood cells. In PNH the defective PIG-A gene produces either too few, or no GPI-anchors, meaning the blood cells are prone to destruction by complement, part of our natural immune system.

The bone marrow contains hundreds of thousands of HSCs but it is only the one (or maybe more than one) that has the PIG-A gene mutation which produces cells without GPI-anchors which are therefore susceptible to destruction. This means that not all the blood cells in a PNH patient will be abnormal; those that come from the remaining HSCs that do not have the PIG-A gene mutation will be normal. In fact, PIG-A gene mutations are common in the general population but do not go on to produce PNH. This is because for PNH to develop there must be a PIG-A gene mutation in a HSC and some degree of bone marrow dysfunction. It is in this context of bone marrow dysfunction that the defective HSC is able to produce relatively more blood cells than the normal HSCs, therefore the proportion of abnormal blood cells increases.

Patient Symptom Diary

Download the diary designed to help you to keep a record of any symptoms or problems you are experiencing due to your PNH. You can also record your hospital appointments and any questions you might like to ask your doctor. The information within your diary can be discussed with your nurse/doctor when you next visit him/her. You may also ask your nurse/doctor to record important information about your illness for you.

Patient Symptom Diary
195 KB

Where can I get more information?

Alexion is not responsible for the content of these independent websites.

Nationally funded PNH Service (England) –

The PNH Service is funded by NHS England to provide specialist support and care to all patients with PNH and their families in the UK. The service is based at two specialist centres: St James’s Hospital, Leeds and Kings College Hospital, London. After you have been diagnosed with PNH, you may be referred to the service by either your local haematologist or GP. Depending on where you live, you will have to option to visit either of the two specialist centres or one of the 12-weekly clinics in Manchester, Liverpool, Peterborough, Birmingham, Bristol, Oxford, Southampton or Lanarkshire. This means members of the PNH Service healthcare team will be able to support you as close to home as possible.


England and Wales


Leeds Teaching Hospitals
NHS Trust

Level 3, Bexley Wing
St James’s University Hospital
Beckett Street
Leeds LS9 7TF

  0113 206 8625

King’s College Hospital
NHS Foundation Trust
Department of Haematology
Hambleden Wing
Denmark Hill
London SE5 9RS

  0203 299 1039



Republic of Ireland
Dr. Catherine Flynn MD
MRCP(Edin) FRCPath
National Speciality Director in
Consultant Haematologist
St James's Hospital,
James's Street,
Dublin 8, Ireland

Northern Ireland
Professor Mary Frances McMulllin
Haematology Dept
Belfast City Hospital
Lisburn Road



Scottish PNH Outreach Clinic
Department of Haematology
Monklands Hospital
Monkscourt Avenue

  01236 712099

01236 712638