PNH National Services


How is PNH diagnosed?

PNH is a rare condition, and it can take time for a diagnosis to be made. PNH is diagnosed by a specific blood test.
Due to the symptoms experienced with PNH some patients may initially have seen a wide range of specialists (for example, urologists, gastroenterologists, cardiologists, neurologists) before it is recognised it is due to a blood and bone marrow problem (and referral to a haematologist).

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 but also provides a target that can be used for effective therapies.

The cells are tested as below. There is a normal flow plot and a flow plot for PNH. As you can see, there are cells lacking the cell surface markers on the bottom flow plot.