Erythrocytosis
Erythrocytosis means too many red cells in the blood; the same thing is often called polycythaemia.
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Erythrocytosis means too many red cells in the blood; the same thing is often called polycythaemia. Red cells carry oxygen, but the more of them there are, the thicker the blood becomes: it flows less easily through small vessels, hands over its oxygen more slowly and clots too readily where it should not. That is where the symptoms come from, and it is where the main danger lies, which is thrombosis. Erythrocytosis is not a diagnosis in itself but a finding on a blood test, and there is always a reason behind it — anything from excess weight and smoking to a disease of the bone marrow. Finding that reason matters far more than «thinning the blood».
How it shows itself
Plenty of people learn about it by chance, from blood taken for something else. Others do have symptoms, and they are fairly recognisable once you know what to look for.
- a heavy head, headaches, ringing in the ears, dizziness;
- blurred vision, floaters, spells of double vision;
- redness of the face, neck, palms and eyes; on brown and black skin it does not show, but the mucous membranes look congested;
- tiredness and sweating, poorer tolerance of exercise;
- raised blood pressure;
- itching after a bath or shower, a very characteristic sign: it starts within minutes of contact with water, lasts up to half an hour and leaves no rash;
- heaviness under the left ribs and feeling full early in a meal, both signs of an enlarged spleen;
- burning, redness and heat in the fingers and toes, worse in warmth: this is erythromelalgia;
- nosebleeds, bleeding gums, bruises with no injury behind them;
- attacks of gout: sudden pain, swelling and redness of a joint, most often at the base of the big toe;
- confusion and unusual forgetfulness in older people.
When help is needed at once
Thick blood is prone to clotting, and clots are what turn a laboratory finding into a threat to life. These signs do not wait until morning — call an ambulance (in Spain, Italy, Portugal, Poland and Ukraine the single European number 112 applies).
- Stroke. The face suddenly droops, an arm goes weak, speech becomes jumbled; sudden loss of vision in one eye; a sudden, exceptionally severe headache.
- Heart attack. Crushing chest pain lasting more than a few minutes, spreading to the arm, neck or jaw, with sweating, nausea and breathlessness.
- Deep vein thrombosis. Swelling, pain, firmness and warmth in one calf or thigh.
- Pulmonary embolism. Sudden breathlessness, chest pain that worsens on breathing in, coughing up blood, fainting, a racing heart.
- Clots in the abdominal veins. A particular hazard of polycythaemia vera: rising abdominal pain, a belly that swells quickly, jaundice. A clot in the veins of the liver or bowel presents as an acute abdomen, and the link with a blood disorder is not spotted straight away.
Where the surplus red cells come from
The causes fall into three groups, and which group a person belongs to determines absolutely everything that follows.
Relative or apparent erythrocytosis. The number of cells is normal, but the volume of plasma — the liquid part of the blood — has fallen, so the concentration in the test looks high. This happens with dehydration, with water tablets, with excess weight, with heavy drinking and in smokers. It is the commonest situation and the most reversible: remove the cause and the figures return to normal.
Polycythaemia vera. Here the bone marrow makes too many cells of its own accord, with no outside signal. In the great majority of cases the culprit is an acquired fault in the JAK2 gene, which arises in blood cells during life and is not inherited. It is a slow-growing blood cancer, and besides the red cells the platelets and white cells are often raised too. It is uncommon, and the average age at diagnosis is around sixty.
Secondary erythrocytosis. The marrow is working properly but is receiving an excessive signal — erythropoietin, the hormone the kidneys release when oxygen is short. The causes include:
- chronic obstructive pulmonary disease and other serious lung conditions;
- sleep apnoea, a common cause and an easily missed one: oxygen dips at night, and all the person knows is that they snore and wake unrefreshed;
- smoking: carbon monoxide takes the place of oxygen, and the body answers by making more cells;
- living at high altitude;
- congenital heart conditions with blue discoloration;
- kidney problems such as narrowing of the renal arteries, cysts, or the period after a kidney transplant;
- tumours that produce erythropoietin: kidney cancer, liver cancer and certain tumours of the cerebellum and womb;
- use of testosterone and anabolic steroids, a cause patients rarely mention and doctors rarely ask about;
- rare inherited variants of haemoglobin or of the erythropoietin receptor, suspected when the count has been high since youth and relatives are affected too.
How the cause is worked out
The starting point is a repeat blood count: a single high haematocrit can simply reflect a shortage of fluid, so the sample is taken again under calm conditions and after rest. A haematocrit and red cell count that stay high are what justify going further. The work-up usually covers:
- a careful history: smoking, alcohol, water tablets, testosterone and supplements, snoring and daytime sleepiness, work at altitude, illness in the family;
- examination, feeling for an enlarged spleen and liver;
- oxygen saturation and, if breathing pauses at night are suspected, a sleep study;
- erythropoietin in the blood: a low level points to polycythaemia vera, a normal or high one to a secondary cause;
- testing for the JAK2 mutation, the key investigation when polycythaemia vera is suspected;
- ferritin: iron stores run down in this condition, and low iron alongside a high haemoglobin is itself a clue;
- an abdominal ultrasound scan to look at spleen, liver and kidneys;
- biochemistry, uric acid, kidney and liver function;
- a bone marrow test, not for everyone but when the picture is unclear or another blood disorder is suspected.
Part of this is arranged by the family doctor, and a haematologist takes over from there.
What is done about it
Treatment has two aims: to reduce the thickness of the blood and to deal with the cause. Which measures are used depends on what has been found.
- Venesection. The quickest way to unload the blood: a unit is drawn off at each session, much as in blood donation. Sessions are frequent at first and then further apart, guided by the haematocrit, with the usual aim of keeping it below 45 per cent. In polycythaemia vera this is the mainstay of treatment.
- Low-dose aspirin. It makes platelets less likely to stick together. It is used in polycythaemia vera and also in other forms when there is heart or vascular disease. The decision rests with the doctor: where there is a bleeding tendency, benefit and risk change places.
- Medicines that slow the marrow down. These are used in polycythaemia vera when venesection alone is not enough, when the risk of clotting is high or the spleen is large. They include hydroxycarbamide, the interferons (preferred in pregnancy and in younger patients) and, if those fail, the Janus kinase inhibitors.
- Removing the cause. Stopping smoking, losing weight, cutting down alcohol, reviewing water tablets, treating sleep apnoea with a positive pressure device, treating lung disease, coming off testosterone or anabolic steroids, treating a kidney tumour. Often that alone brings the counts back to normal with no need for haematology at all.
- The other risks. Blood pressure, cholesterol, blood sugar, keeping active and avoiding long periods of sitting still count for more here than usual.
- The symptoms. For itching it helps to shower cool rather than hot, to use emollients and antihistamines; if it is stubborn, the underlying disease is treated. Gout is managed separately.
What happens next depends on the cause. Relative and secondary erythrocytosis resolve once the cause is dealt with and do not shorten life. Polycythaemia vera stays for good, but with the haematocrit controlled people live with it for decades; the main threat is clotting, and the whole of treatment is aimed at preventing it. In some patients the marrow is gradually replaced by scar tissue over the years (myelofibrosis), and then blood cells become scarce instead; rarely the disease turns into an acute leukaemia. That is why blood tests continue at regular intervals even when all is well.
Online consultation
Erythrocytosis is a very suitable reason for a video appointment: almost all the work here is done with documents and questions. The doctor looks at several years of results rather than the latest line alone, and judges whether the figure is climbing or merely fluctuating. Everything that might have thickened the blood is gone through with you: smoking, alcohol, water tablets, testosterone and sports supplements, snoring with pauses at night. You will be told which tests are worth having before seeing a haematologist — erythropoietin, the JAK2 mutation, ferritin, an abdominal scan — so that the specialist appointment is not spent arranging them. If a mutation has been found, what it means is explained. Where the diagnosis is already made, the appointment helps with understanding the prescribed treatment, its side effects and the monitoring schedule, and covers pregnancy and travel. And the signs of a clot are spelled out plainly: those call not for a remote appointment but for an ambulance.
This material is for information only and does not replace medical advice.
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