The different types of anaemia
The most common types of anaemia are:
- Iron-deficiency anaemia
- Aplastic anaemia
- Haemolytic anaemia
- Sickle cell anaemia
- Pernicious anaemia
- Fanconi anaemia
- Anaemia of chronic disease
1. Iron-deficiency anaemia
This is the most common cause of anaemia. Iron is a crucial component of haemoglobin and so, if the body’s stores have been depleted, haemoglobin cannot be manufactured at the rate required by the body. Anaemia will be the result.
The body becomes deficient in iron from:
- Insufficient dietary intake to match the body’s needs
- Problems with the absorption of iron from the intestine
- Excessive loss of blood (e.g. through heavy menstruation, childbirth or bleeding stomach or intestinal ulcers), leading to the depletion of the body’s iron stores as the bone marrow tries to replace lost red cells
Iron-deficiency anaemia is mainly seen in:
- Women of child-bearing age (it can affect up to 1 in 5 women)
- Individuals from middle- and low-income countries
- Older adults (over 65 years)
In times of increased demands for iron, such as foetal growth in pregnancy, and children undergoing rapid growth spurts in infancy and adolescence, iron-deficiency anaemia can also result if dietary iron intake isn't increased.
Worm infestation in children can also lead to iron deficiency.
This type of anaemia is treated with iron supplementation as well as the treatment of the underlying cause of the iron deficiency.
The word “thalassaemia” is derived from the Greek word “thalassa”, meaning “sea” (in Greek mythology, Thalassa was the primeval spirit of the sea).
This is because the condition was first described in people of Mediterranean ethnicities. It also tends to occur where Malaria is endemic. Thalassaemias affect both men and women, and occur most often in people of Italian, Greek, Middle Eastern, Asian and African descent.
Thalassaemias are a group of genetic blood disorders that are inherited from a parent who either has the disease or is a carrier of the gene (meaning they don’t have the disease and may be unaware of the abnormal gene that they carry). The abnormal gene causes reduced production of either the alpha or beta chains that form part of the haemoglobin molecule.
This prevents normal haemoglobin formation with fewer healthy red cells released into the circulation.
The abnormal red cells that are formed are destroyed by organs such as the spleen before their normal 120-day lifespan is up. Because of the anaemia that results from the destruction of the red blood cells, the body sends signals to:
1.) the bone marrow to increase red cell production; and
2.) the digestive tract to increase iron absorption in an attempt to produce more haemoglobin.
This can lead to “iron overload”, which in itself is dangerous to the heart, liver and kidneys.
Thalassaemia is a lifelong condition with which you’re born. It differs in severity and presentation, depending on the amount and type of abnormal haemoglobin chains produced.
The two major types of thalassaemia are alpha- and beta thalassaemia. The most severe form of alpha thalassaemia is known as “alpha thalassaemia major” (hydrops fetalis), while the severe form of beta thalassaemia is known as “thalassaemia major” (Cooley's anaemia).
There’s been a shift in the way that thalassaemias are classified and they’re now mainly seen as “transfusion dependent” or “transfusion independent”, depending on whether they’re severe enough to warrant regular blood transfusions as therapy.
People affected by the condition may be asymptomatic carriers of the abnormal gene or develop symptoms and signs of anaemia in infancy or early childhood.
- Symptoms of severe anaemia
- Abnormal-appearing bones of the skull and face
- Abdominal swelling from enlargement of the liver and spleen
- Symptoms of iron overload
- Growth impairment
- Blood clots
- Leg ulcers
Thalassaemia can be suspected in an infant or child with a family history of the condition. However, a negative family history doesn’t rule out the diagnosis, as both parents may only be carriers of the affected gene and unaware of the condition.
Diagnostic testing includes an initial full blood count, examination of the red cells under a microscope (called a “blood smear”), and iron studies.
The red cells in thalassaemia are small (microcytic), abnormally shaped (target cells and teardrop-shaped cells are seen), and there may be inclusions in the red cells seen under a microscope, which represent the unpaired haemoglobin chains. There may also be a high red cell count. Iron studies may show elevated serum iron and ferritin levels.
The diagnosis is confirmed with a haemoglobin analysis, which will show abnormal haemoglobin; as well as genetic testing for the abnormal globin gene. Genetic testing can be offered to women and men wishing to conceive if a first-degree relative is affected. This will determine whether they’re carriers of the abnormal gene, and counselling can be provided about the chances of future children being affected.
3. Aplastic anaemia
There are three types of cells found in the blood:
- Red cells, which carry oxygen around the body
- White cells, which fight infections
- Platelets, which form clots when you’re bleeding.
All three are produced by the bone marrow.
Aplastic anaemia occurs when the bone marrow is damaged and fails to produce enough of all three cell types.
The features of aplastic anaemia include:
- Symptoms of anaemia due to reduced red cells
- Recurrent or severe infections due to reduced white cells
- Bleeding tendency due to lack of platelets
Aplastic anaemia is a rare but serious condition. It can develop suddenly or slowly, and tends to worsen with time, unless the cause is found and treated.
4. Haemolytic anaemia
Haemolytic anaemia is a condition in which red blood cells are destroyed and removed from the bloodstream before their normal lifespan is up.
This can be because the cells have some abnormality that prompts the body to remove them from the circulation or, in the case of autoimmune haemolytic anaemia, because the body recognises the cells as foreign and destroys them.
Red blood cells can also be mechanically damaged and destroyed. This happens, for example, in some individuals who have prosthetic heart valves.
This type of anaemia is unique in that it may cause jaundice (yellow discolouration of the whites of the eyes and skin) and dark urine from the accumulation of breakdown products of red cells.
The liver and spleen may also be enlarged, as these are the organs responsible for removing abnormal red blood cells from the circulation.
There are many causes of haemolytic anaemia – some of which are inherited/genetic and others that are acquired.
Inherited haemolytic anaemias include:
- Sickle cell anaemia
- Hereditary spherocytosis
- Hereditary elliptocytosis
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency
- Pyruvate kinase deficiency
Acquired haemolytic anaemias include:
- Immune haemolytic anaemia:
- Autoimmune haemolytic anaemia
- Alloimmune haemolytic anaemia
- Drug-induced haemolytic anaemia
- Mechanical haemolytic anaemias
- Paroxysmal nocturnal haemoglobinuria
Certain infections and substances can also damage red blood cells and lead to haemolytic anaemia.
Depending on how rapidly the anaemia develops, blood testing may show an elevated reticulocyte count (increased number of immature red cells released from the bone marrow) and there may be indicators of an increased breakdown of red cells: elevated bilirubin levels, increased lactacte dehydrogenase, and low haptoglobin.
If the breakdown of red cells is slow and chronic, these tests may be normal.
To diagnose autoimmune haemolytic anaemia, a direct antiglobulin test (Coombs test) is performed. Further testing depends on the suspected cause, which includes genetic testing for specific red cell enzyme defects.
5. Sickle cell anaemia
Sickle cell anaemia is a genetic disease in which the body makes sickle-shaped (“C”-shaped) red blood cells due to the production of abnormal haemoglobin.
Normal red blood cells are disk-shaped and move easily through the blood vessels. Sickle-shaped cells don’t move easily through the blood vessels – they’re stiff and sticky, and tend to form clumps and get stuck in the blood vessels, causing blockage of blood flow to the limbs and organs.
People with this condition suffer from “sickle cell crises” – episodes of acute pain due to occlusion of blood vessels.
In sickle cell anaemia, a lower-than-normal number of red blood cells occurs because sickle cells don’t last very long. Sickle cells usually die after about 10 to 20 days, and the body can’t reproduce red blood cells fast enough to replace the dying ones, which causes anaemia.
6. Pernicious anaemia
Another important “ingredient” needed for haemoglobin production is vitamin B12.
In order for vitamin B12 to be absorbed from the digestive tract, it’s paired with a protein produced in the stomach called “intrinsic factor”. If there’s an absence of intrinsic factor, vitamin B12 cannot be absorbed, haemoglobin cannot be adequately manufactured, and anaemia will result.
Pernicious anaemia is an autoimmune condition caused by antibodies directed against intrinsic factor. It’s associated with other autoimmune conditions such as vitiligo, as well as an increased risk of gastrointestinal cancer.
The diagnosis is made by measuring vitamin B12 levels and testing for the antibody directed against intrinsic factor.
7. Fanconi anaemia
Fanconi anaemia (FA) is a rare inherited blood disorder that leads to inability of the bone marrow to produce blood cells.
It’s a type of aplastic anaemia that prevents your bone marrow from making enough new blood cells for your body to work normally. FA can also cause your bone marrow to make abnormal blood cells, which can lead to serious health problems such as leukaemia.
FA is a blood disorder, but it can also affect many of the body’s organs, tissues, and systems. Children who inherit FA are at higher risk of being born with birth defects, and people who have FA are at higher risk of some cancers and other serious health problems.
FA is an unpredictable disease. The average lifespan for people with FA is between 20 and 30 years. The most common causes of death related to FA are bone marrow failure, leukaemia, and solid tumours.
8. Anaemia of chronic disease
This is anaemia that’s associated, through various mechanisms, with conditions such as:
- Chronic inflammatory conditions
- Chronic kidney disease
- Severe trauma
- Chronic immune activation
Anaemia of chronic disease is mainly due to reduced production of red blood cells by the bone marrow, and is usually a mild form of anaemia.
Reviewed by Cape Town-based general practitioner, Dr Dalia Hack. October 2018.