Anaemia is a result of reduced haemoglobin in the blood. This could be due to a defect in red blood cell production or due to accelerated destruction.
Destruction of red blood cells is also termed haemolysis. Hence the term haemolytic anaemia is used when the anaemia occurs due to increased haemolysis.
Pathophysiology and Classification
This premature destruction could be due to defects in the structure and function of the erythrocytes themselves or due to external factors predisposing to haemolysis.
Inherent defects, which are also called intracorpuscular abnormalities, are often hereditary, and the problem could be in the red blood cell membrane, haemoglobin molecules, or intracellular enzymes.
- Hereditary spherocytosis is a form of haemolytic anaemia resulting from a membrane defect. As the name suggests, cells lose their normal biconcave shape and become spherical. These abnormal red cells are more likely to be destroyed.
- A well-known haemoglobin abnormality causing haemolytic anaemia is sickle cell anaemia.
- Glucose 6 phosphate dehydrogenase deficiency or G6PD deficiency is also an important cause of haemolytic anaemia as it is the most common enzyme deficiency in the world. It is an important enzyme found in red blood cells which protects the cell membrane against oxidative damage.
External factors or extracorpuscular abnormalities are usually acquired in later life.
These types of haemolytic anaemias, like autoimmune haemolytic anaemia, are mostly antibody mediated.
Antibodies attack parts of the red blood cell membrane leading to haemolysis.
Antibody production could either be due to an unknown cause or secondary to other disease conditions like chronic lymphoid leukaemia, malignant lymphoma, and Systemic lupus erythematosus.
The haemolytic process in haemolytic anaemias could either occur within the vasculature or outside, allowing us to classify it as intravascular and extravascular.
Extravascular haemolysis occurs generally in the spleen, mediated by splenic macrophages.
The released haemoglobin is converted to a substance called bilirubin before being released into the blood. At increased levels, bilirubin can deposit in your eyes to give them a yellow tinge, which is called jaundice.
The serum bilirubin level can also be measured to help with the diagnosis process.
When the haemolysis is intravascular, haemoglobin is released directly into the bloodstream.
This free haemoglobin binds to a plasma protein called haptoglobin, thus decreasing the free haptoglobin level in blood.
Free haemoglobin can also get oxidized to form methaemoglobin, which can bind withalbumin to form methemalbumin. Haptoglobin and methemalbumin levels can be used as markers to detect intravascular haemolysis.
Full blood count and blood picture are done as initial tests to confirm the presence of anaemia. These are non-specific and the results may vary depending on the type of haemolytic anaemia.
As haemolytic anaemias are a group of disorders, specific laboratory investigations directed at confirming or excluding each cause should be conducted.
special tests used in the detection of the diseases
- Hereditary spherocytosis – osmotic fragility testing
- Sickle cell anaemia – haemoglobin electrophoresis
- G6PD deficiency – G6PD screening test
- Autoimmune haemolytic anaemia – Coomb’s test
Treatment
Treatment may include, but is not limited to, blood transfusions, splenectomy, and the use of immunosuppressive agents in the case of immune-mediated conditions. it largely depends on the type of anaemia.
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