Medicines for Erythrocytosis

What it is

Erythrocytosis (also called polycythaemia) is a condition in which there is a higher-than-normal number of red blood cells in the blood. Red blood cells carry oxygen around the body; having too many of them makes the blood thicker, which can affect the flow of blood and, if significant, increase the risk of problems such as blood clots. Erythrocytosis is often found on a blood test (which shows a raised red cell count or related measures, such as haemoglobin or haematocrit), sometimes when investigating symptoms or by chance. It is important because it can be a sign of an underlying cause, and because significant erythrocytosis carries risks that may need managing. There are broadly two main categories. Secondary (or relative/apparent) erythrocytosis is where the raised red cell count is a response to another factor, or is apparent rather than a true increase in cell numbers — causes include a lack of oxygen in the body (which stimulates red cell production), for example due to lung or heart conditions, sleep apnoea, smoking, or living at high altitude; kidney or other conditions; certain medicines or substances; and dehydration or other factors causing the blood to appear more concentrated (apparent erythrocytosis). Primary erythrocytosis is where the problem is in the bone marrow itself producing too many red cells — the main example being a condition called polycythaemia vera (a type of blood disorder), which is less common but important. The symptoms of erythrocytosis, if present, can include headaches, dizziness, tiredness, blurred vision, redness of the skin (particularly the face), itching (especially after a warm bath, in some cases), and, if it leads to clots, symptoms of these. However, it may cause no symptoms and be found on a blood test. Because the causes and their significance differ greatly, an important part of care is identifying the cause of the erythrocytosis, as this determines the treatment — for secondary causes, treating or addressing the underlying cause (such as a lung condition, sleep apnoea, or smoking) is key; for primary causes (such as polycythaemia vera), specific treatment and specialist care are needed. Managing significant erythrocytosis may also involve reducing the risk of clots. The key messages are that erythrocytosis is a raised red blood cell count that thickens the blood, that the cause guides treatment (it can be a response to another factor, or, less commonly, a blood condition), and that identifying and managing the cause, and any risks, are important.

How it is treated

Erythrocytosis is managed by identifying the underlying cause (which guides treatment), treating or addressing that cause, and, where relevant, managing the risks (such as of clots); the approach differs greatly between secondary causes and primary blood conditions. When erythrocytosis is found (often on a blood test), an important step is assessment to identify the cause — this involves the history and examination, further blood tests, and investigations guided by the likely cause, which may include checking for causes of low oxygen (such as lung or heart conditions, or sleep apnoea), assessing smoking, checking the kidneys and other possible causes, and, importantly, tests to look for a primary blood cause such as polycythaemia vera (including specific blood tests and, where relevant, a genetic test and bone marrow assessment), guided by specialists (such as haematologists) where needed; sometimes an apparent (relative) erythrocytosis due to concentration of the blood is distinguished from a true increase. The treatment then depends on the cause. For secondary erythrocytosis (a response to another factor), the key is treating or addressing the underlying cause — for example, treating a lung or heart condition, treating sleep apnoea, stopping smoking (which is a common and important contributor, and stopping it can improve the count), and addressing other causes; this often improves or resolves the erythrocytosis. For apparent (relative) erythrocytosis, addressing contributing factors (such as fluid balance, smoking, and lifestyle factors) is relevant. For primary erythrocytosis, particularly polycythaemia vera, specific treatment and specialist (haematology) care are needed — this may include treatments to reduce the number of red cells and control the condition, and, importantly, measures to reduce the risk of blood clots (such as a treatment to thin the blood, and removing blood/venesection to reduce the red cell count in some cases), as polycythaemia vera carries a risk of clots; ongoing specialist monitoring and management are provided. Managing the risk of clots is an important consideration in significant erythrocytosis generally. Lifestyle measures — such as not smoking, staying well hydrated, and managing cardiovascular risk factors — support management and reduce risks. The reassuring messages are that erythrocytosis is often due to an identifiable and treatable cause (such as a response to low oxygen, smoking, or another factor), that identifying the cause is key (as it guides treatment), and that, for the less common primary blood causes (such as polycythaemia vera), specific treatment and specialist care are available to manage the condition and reduce risks; so assessment to find the cause, treating or addressing it, and managing any risks are the keys to managing erythrocytosis.