Causes of anaemia

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Anaemia causes, classified by size and amount of red blood cell found in samples taken from the patient. So you get three types, microcytic (small cells), normocytic (normal cells) and macrocytic (big cells). This is measured in the mean corpuscular volume (MCV) - the normal range is 70-96.


Iron deficiency


This is the most common cause of microcytic anaemia. Babies are more at risk than adults, because a baby needs almost as much daily iron as an adult, but eats much much less. Thus, a low iron intake (diet) can have a rapid effect.

Commonly this can happen by substituting breast milk with cow’s milk without adding formula. Cow’s milk has 1/5 of the iron of breast milk. For the weaned child, having low iron foods can be the cause. Give advice about this to vegetarian parents.

Iron deficiency is the only cause of koilonychia (spoon shaped nails), so look for that. Another symptom of iron deficiency anaemia is pica, which is eating non food stuffs, like soil, gravel, umbrellas and small buildings. This is something toddlers do, presumeably trying to get iron from stuff. Worth asking about in the history though!

First here is the normocyte, or a normal blood cell. Nice, eh? Next is the reticulocyte, seen in haemolysis. Next up is the spherocyte, which, as is the key cause of hereditary haemolysis. Finally is the sickle cell, which is seen in sickle cell disease, unsurprisingly.



Various types, but the severe version, β-thalassaemia major causes jaundice and anaemia from 6 months of age. There will be liver and spleen enlargement also. Without regular blood transfusions this condition is fatal. In the milder versions, its less of a problem, but always have it in the back of your mind, since it can be mistaken for iron deficiency anaemia.

Sickle Cell Disease


This is a hereditary condition, where there are two manifestations. In hetrogynomy### (HbS) the child will be unlikely to present, and will have some protection against malaria. In homozygous### (HbSS) sickle cell inheritance, the child will have malformed haemoglobin, with a reduced red cell lifespan, and more risk of clots.

This is a risk of anaemia in HbSS, due to haemolysis of the weird shaped cells. There is also common occurrences of episodes of pain, generally in the peripheries. However there can be necrosis of any organ or body part, due to clots from the rubbish cells!

For kids, the big worry is for pneumoccal infection, due to the spleen breaking down. Thus penicillin should be taken throughout life. Although 85% of people with the full disease live past 20, most of the 15% die under the age of 3, due to infection.

Rarer causes


Sideroblastic anaemia (the body has iron but cannot incorporate it into haemoglobin - prediposes to haematological malignancies); lead poisoning; and pyrodoxine deficiency.


Blood loss


Acute:This is a common cause of shock, but in most cases, it will be obvious (“This man has just lost an arm, and there’s blood squirting all over the floor – AND he’s anaemic?! Maybe we should check for B12 deficiency…?”). Treatment is threefold: stop the blood loss, treat the shock and replace the blood through transfusion.

Chronic: Gastric ulcers and cancers often cause asymptomatic bleeding. Thus anaemia is always a potential cause for concern.

Anaemia of chronic disease


Commonly with any long term infection, inflammation and malignancy, the liver can make extra Hepcidin, which is some chemical that makes the body less good at making irony blood (irony: n.; The use of words expressing something other than their literal intention). This gives people a (usually) mild normocytic anaemia.

Aplastic anaemia


Basically, this is anaemia where red cells are not being made. You will most commonly see it in leukaemia patients in remission, who have had treatment that has knocked out the bone marrow.

Treatment, short term, is transfusion. Without this, the patients will die. Long term, bone marrow transplant is the best cure. The other key causes are:

Other haemolytic anaemias


Aside from Sickle Cell, and Thalassaemia, the main anaemia associated with haemolysis is the memorably named Glucose-6-phosphate dehydrogenase deficiency. Its very common (100 million+ worldwide), although most are not badly affected.

In males, or homozygous/lyonised females, it causes episodes of haemolysis. What happens is the missing enzyme makes the blood cells more vulnerable to oxidation, and they end up getting taken to the spleen and mashed up. Treatment of it involves avoiding foods and drugs that make this more likely. When it happens, it needs to be treated with transfusion.

Endocrine disorders


Stuff like hypopituitarism, and paediatric thryoid disorders can cause anaemia, so worry about these if everything else fails.




Haemolysis due to another cause, such as auto-immune disease, can cause macrocytic anaemia, because the bone marrow goes into production overload, releasing red cells that aren't fully matured (reticulocytes), and are big and blobby. Sadly, such young cells are also rubbish at holding oxygen, so its not ideal. Drugs and neoplasia can cause haemolysis.

Pernicious anaemia/B12 deficiency


Pernicious anaemia is an anaemia caused by malabsorption of Vitamin B12 due to non production of intrinsic factor from the parietal cells in the stomach. The most common B12 deficiency comes from Crohn's disease, or anything that messes up the end of the ileum. Big link to alcoholism - or being vegan.

Often presents with fatigue, numbness, and if it gets bad, an ataxic gait. Treatment is by increasing the amount of B12 in the diet, intravenous B12 and treatment of the underlying cause. Also treated with hydroxocobalamin.