Polycythaemia, or erythrocytosis, means having a high concentration of red blood cells in your blood. See your GP if you have persistent symptoms of polycythaemia. You should also get emergency medical help if you think you or someone you're with is having a heart attack or stroke.
Symptoms of polycythaemia
A high concentration of red blood cells in your blood makes the blood thicker and less able to travel through blood vessels and organs.
Many of the symptoms of polycythaemia are caused by this sluggish flow of blood.
Mild cases of polycythaemia may not cause any problems, but some people with polycythaemia can experience:
- discomfort in the chest or tummy (abdomen)
- muscle ache and weakness
- headaches - may be experienced as a sense of 'fullness' in the head and neck
- tinnitus - hearing sounds that come from inside your head, when there is no sound externally
- blurred vision (or temporary loss of vision in one or both eyes)
- paraesthesia - an abnormal sensation such as tingling, tickling, pricking, numbness or burning, with no clear physical cause
- periods of confusion
- bleeding problems – such as nosebleeds, heavy periods and bruising
- itchy skin – especially after a bath or shower - this is the result of white blood cells (levels of which can also be high) releasing the chemical histamine
- red skin – particularly in the fingers, palms, heels or toes
- gout – which can cause joint pain, stiffness and swelling
You should make an appointment to see your GP if you have persistent symptoms of polycythaemia.
When to get immediate medical advice
The slow blood flow associated with polycythaemia can also cause blood clots.
These can be serious because they may put you at risk of life-threatening problems such as:
- heart attacks
- pulmonary embolisms – a blockage in the blood vessel that carries blood from the heart to the lungs
In some cases, a blood clot – known as deep vein thrombosis (DVT) – may form in your leg, before moving elsewhere in your body.
Signs of DVT or a pulmonary embolism can include:
- pain, swelling, redness and tenderness in one of your legs
- a heavy ache in the affected area
- warm skin in the area of the clot
- chest or upper back pain
- coughing up blood
- feeling lightheaded or dizzy
If you experience any of the above symptoms, seek medical help immediately.
You should also seek emergency medical help if you think that you or someone you are with is having a heart attack or stroke.
Causes of polycythaemia
Polycythaemia can be divided into several different types, depending on the underlying cause of the condition. In some cases, an underlying cause can't be identified.
’Apparent polycythaemia’ is where your red cell count is normal, but you have a reduced amount of a fluid called plasma in your blood, making it thicker.
The condition is often caused by being overweight, smoking, drinking too much alcohol or taking certain medications – such as diuretics for high blood pressure.
A similar condition that's sometimes called ’relative polycythaemia’ can also occur as a result of dehydration.
‘Absolute polycythaemia’ is where your body produces too many red blood cells. There are two main types:
- primary polycythaemia – there's a problem in the cells produced by the bone marrow that become red blood cells; the most common type is known as polycythaemia vera (PV)
- secondary polycythaemia – too many red blood cells are produced as the result of an underlying condition
Both PV and secondary polycythaemia are described in more detail below.
Polycythaemia vera (PV)
PV is a rare condition usually caused by a fault in the JAK2 gene. The condition causes the bone marrow cells to produce too many red blood cells.
The affected bone marrow cells can also develop into other cells found in the blood. This means that people with PV may also have abnormally high numbers of both platelets (thrombocytosis) and white bloods cells (leukocytosis).
Although caused by a genetic fault, PV isn't usually inherited. Most cases develop later in life, with 60 the average age of diagnosis.
Secondary polycythaemia is where an underlying condition causes more erythropoietin to be produced.
This is a hormone produced by the kidneys that stimulates the bone marrow cells to produce red blood cells.
Conditions that can cause secondary polycythaemia include:
- chronic obstructive pulmonary disease (COPD) and sleep apnoea – these can cause an increase in erythropoietin, due to not enough oxygen reaching the body's tissues
- a problem with the kidneys – such as a kidney tumour or narrowing of the arteries supplying blood to the kidneys
How polycythaemia is diagnosed
Polycythaemia can be diagnosed by carrying out a blood test to check:
- the number of red blood cells in your blood (red blood cell count)
- the amount of space the red blood cells take up in the blood (haematocrit level)
A high concentration of red blood cells suggests you have polycythaemia.
Your GP may have ordered a blood test because you reported some of the above symptoms or complications.
But polycythaemia is sometimes only discovered during a routine blood test for another reason.
Your GP may refer you to a haematologist (a specialist in conditions affecting the blood) for more tests, to confirm the diagnosis and to work out the underlying cause.
These may include a blood test to look for the faulty JAK2 gene and an ultrasound scan of your abdomen to look for problems in your kidneys.
Treatment for polycythaemia aims to prevent symptoms and complications (such as blood clots), and treat any underlying causes.
Treatment can include:
- regular removal of blood to reduce the amount of red blood cells in your body
- medication to reduce the production of red blood cells
- medication to prevent blood clots
The health professional looking after your care will discuss the most appropriate treatment option with you.
Treating and preventing other conditions
Some people may also need treatment for any other symptoms or complications of polycythaemia they have, or for any underlying cause of the condition.
For example, you may be given medication to help relieve itching, manage COPD or treat gout.
As well as improving some cases of apparent polycythaemia, making healthy lifestyle changes can also reduce your risk of potentially serious blood clots for people with all types of polycythaemia.
The outlook for polycythaemia largely depends on the underlying cause.
Many cases are mild and may not lead to any further complications. Some cases – particularly cases of PV – can be more serious and require long-term treatment.
If well controlled, polycythaemia shouldn't affect your life expectancy, and you should be able to live a normal life.
People with PV can have a slightly lower life expectancy than normal due to the increased risk of problems, such as heart attacks and strokes.
PV can also sometimes cause scarring of the bone marrow (myelofibrosis). This can eventually lead to you having too few blood cells. In some rare cases, the condition can develop into a type of cancer called acute myeloid leukaemia (AML).
If you have polycythaemia, it's important to take any medication you're prescribed. It is also important to keep an eye out for signs of possible blood clots to help reduce your risk of serious complications.
More useful links
The information on this page has been adapted from original content from the NHS website.
For further information see terms and conditions.