Paroxysmal nocturnal haemoglobinuria (PNH)

Paroxysmal Nocturnal Haemoglobinuria (PNH) is an extremely rare autoimmune condition. It is a potentially life-threatening blood disease and is estimated to affect around 16 people per million in the UK.¹

What is PNH?

PNH is an acquired, rare, chronic, blood disease commonly characterised by persistently low haemoglobin, thrombosis and debilitating symptoms. It occurs when the cells in the bone marrow responsible for making red blood cells (which help to carry oxygen around the body) mutate and produce defective blood cells.²  When this happens, the immune system is triggered to attack and destroy the red blood cells. The premature destruction of red blood cells is known as haemolysis. Red blood cells in a healthy individual last about 120 days before being broken down naturally in the body.³  People with PNH experience premature destruction of red blood cells.⁴

Why is it called paroxysmal nocturnal haemoglobinuria?

The term PNH was coined in the early 20th century, based on a description of the symptoms observed in patients.

• Paroxysmal refers to symptoms occurring intermittently or suddenly.
• Nocturnal refers to the fact that it seems to occur at night (or to be observed first thing in the morning).
• Haemoglobinuria refers to haemoglobin seen in urine (discolouring it dark red or black).

The term can be misleading for some people who have PNH because, in reality, the condition is present all the time and not everyone experiences dark urine.⁵

How is PNH diagnosed?

It can take a long time to make a diagnosis of PNH as it is a very rare illness that many doctors will not be familiar with. Many of the symptoms of PNH are common to numerous other diseases; because of the wide range of symptoms they might have, PNH patients may initially be seen by a wide range of specialists (such as urologists, cardiologists and neurologists) before their condition is recognised as a blood and bone marrow problem so they can be referred to a haematologist.

Initial diagnosis

PNH may be confirmed by a specific blood test, flow cytometry, which identifies PNH cells (blood cells that are missing specific proteins known as GPI-anchored proteins) and measures the proportion of PNH red blood cells within a patient’s blood.⁷

Ongoing diagnosis

Doctors may recommend further flow cytometry testing to monitor progression. In addition, there are two other laboratory tests for monitoring the disease:

• Lactate dehydrogenase (LDH). ⁷ LDH is an enzyme present in red blood cells. This test gives an indication of how much haemolysis is going on in the patient’s body.
• Full blood count (FBC). ⁷ The FBC indicates the counts of white blood cells, red blood cells and platelets, and the concentration of haemoglobin. In addition, it can help to identify bone marrow abnormalities.

How can people living with PNH improve their lives?

Understanding the science behind PNH, symptoms and treatment can help someone living with PNH to gain insights about their health and care, as well as support communication with their healthcare teams in terms of sharing individual symptoms, PNH-related goals and ambitions for everyday life and goals for the future.

A support network may help people achieve those goals. Support can come from different corners of life and can include family, friends, patient advocacy groups or external resources.

Discussions with the treating consultant or involvement with patient advocacy groups can be an opportunity for new insights and support for patients wishing for change.