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Anaemia

A disease of the blood

This is article no. 1 in a series about anaemia. Next article: iron-deficiency anaemia


Introduction


Erythrocytes in their typical state are a biconcave and nucleus free cell responsible for carrying oxygen and carbon dioxide. The production is controlled by erythropoietin and as they mature in the bone marrow, they lose their nuclei. These red blood cells (RBC) contain haemoglobin, which aids in the transport of oxygen and iron, iron is a key component of haem, insufficient levels of iron leads to anaemic disorders. Low oxygen-carrying capacity may be defined by too few RBC in circulation or RBC dysfunction. Haem iron is acquired through the digestion of meat and transported through enterocytes of the duodenum, in its soluble form.


Erythrocytic iron accounts for approximately 50% of the iron in blood. Metals cannot move freely throughout the body so they must be transported, the molecule involved in transporting iron is known as transferrin. Plasma transferrin saturation refers to the iron that is attached to transferrin, in iron deficient anaemia (IDA) this will always be low. Anaemia is physiological or pathological, these changes can be due to a plethora of causes; malabsorption due to diet or gastrointestinal (GI) conditions, genetic dispositions such as sideroblastic anaemias (SA), thalassaemia, or deficiency in erythropoietin due to comorbidities and chronic disease; where haemolysis is caused by autoimmune disorders, infections and drugs, or blood loss.


Haem


The iron is in a protoporphyrin ring at the centre of a haem molecule. The structure of haem consists of two alpha and two beta polypeptide chains to form a single haemoglobin macromolecule. Microcytic anaemias arise from problems in the creation of haemoglobin; sourcing through diet (IDA), synthesising protoporphyrin (SA) or from globin chain defects caused by thalassaemia.


Summary


Anaemia is a multifactorial condition with many different mechanisms involved, microcytic anaemias have an issue at the haemoglobin level, these can be acquired or inherited. A microcytic anaemia is caused by a failure to efficiently synthesise haemoglobin, whether from iron, protoporphyrin rings or globin chains. The diagnosis of anaemias is reliant on a patient’s background and medical history, as there are many factors involved in an anaemic disorder. A diagnosis should be patient led, as the age and sex of the patient can significantly highlight the origin and pathogenesis, as well as the prognosis and follow up care.


 By Lauren Kelly


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