How is PNH diagnosed?

It can often take a long time to make a diagnosis of PNH as it is a very rare illness that many doctors will only come across a few times, if ever, in their career. It is not uncommon for PNH patients to be initially seen by a wide range of specialists (for example, urologists, gastroenterologists, cardiologists, neurologists), due to the range of different symptoms with which the condition can present, before it is recognised it is due to a blood and bone marrow problem (and referral to a haematologist). PNH is diagnosed by a specific blood test.

When someone is diagnosed with PNH in the UK they will normally be seen by a haematologist at their local hospital who may choose to refer the patient to the National PNH Service in Leeds or London.

What is a PNH clone?

A clone is a group of cells identical to each other. The term “PNH clone” is often used and refers to the proportion (percentage) of blood cells that are PNH rather than normal. In general, the larger the proportion of PNH cells the more likely that person will have symptoms of the disease but there are exceptions. The cells derived from the PNH stem cell are deficient (lacking) in a number of proteins on their surface. The most relevant of these in PNH are a couple of proteins that protect our own cells from attack by a component of our immune system, called complement. This means that PNH cells are exquisitely sensitive to attack by our own complement and this leads to many of the symptoms of PNH (see above) but also provides a target that can be used for effective therapy (eculizumab).