Discuss and explain the differences between anaemia resulting from iron deficiency and that resulting from vitamin B12/ folic acid deficiency
Blood is the life sustained fluid, it is composed of a complex mixture of three formed cellular elements erythrocytes, leukocytes and thrombocytes suspended in a viscous fluid known as blood plasma. Erythrocytes are the most numerous blood cell types. They are produced through a process involving complex and specific steps, then after maturation they are released into the blood stream where they survive for approximately 120 days. Erythrocytes lack nuclei, have a biconcave discoid shape, with an 8 µm in diameter and contain haemoglobin (a pigmented protein) responsible for gaseous exchange and oxygen delivery to the tissues (Pallister, 2001). Each erythrocyte contains about 640 million haemoglobin (Hb) molecules, each of those are composed of four polypeptide chains (two alpha-? ?and two beta-?, in normal adults). Additionally, each chain is associated with one iron containing a haem molecule that is able to bind to one oxygen molecule, therefore together each haemoglobin molecule is able to bind four oxygen molecules (Hughes-Jones, 2004). Anaemia is said to be present when levels of Hb concentration (with or without the concomitant decrease in erythrocytes) fall below the reference range (table 1). Moreover, anaemia can be classified into three major types according to the size of erythrocytes, these are known as microcytic hypochromic anaemia (when erythrocytes size is smaller and paler than normal), macrocytic anaemia (erythrocytes larger than normal) and normocytic anaemia (erythrocytes size is normal however low in number) (Hoffbrand, 2006). Anaemia accomplishes several symptoms however the most common are weakness, shortness of breath, tiredness, palpitations and headaches.
This essay will highlight two types of anaemia, resulting from iron deficiency and that resulting from vitamin B12/ folate deficiency.
Although iron is widely distributed in the Earth’s crust, anaemia due to iron deficiency is by far the most major cause of microcytic hypochromic anaemia worldwide (due to body’s limited ability to absorb iron and excess loss of iron) and may result from at least four conditions (table 2). In this type of anaemia, the MCV (mean corpuscular volume) and MCH (mean corpuscular haemoglobin) are reduced and examinations on the blood film characteristic reveals small-microcytic and pale-hypochromic erythrocytes. This is due to defects in haemoglobin synthesis (Hoffbrand, 2006). Additionally, there are other haematological findings that are associated with this type of anaemia for instance, platelets that are usually normal may increase due to acute blood loss, leukocyte count is generally normal, and reticulocyte count and osmotic fragility may be normal or decreased. Furthermore, bone marrow examinations may also show a noticeable decrease in stainable iron and erythroid hyperplasia. Clinical chemistry analysis is normally used to access iron status and this includes serum iron, total iron-binding capacity, percentage saturation and serum ferritin (Turgeon, 2005). Iron plays a crucial role in the normal function and metabolism of various cells in the body, therefore absorption and distribution of iron throughout the body must be highly regulated (Fig.1). These is determined largely by the activities of three iron transport and storage proteins known as transferring-Tf (a ? globulin able to carry two atoms of iron), transferring receptor (TfR1) and ferritin (water-soluble protein-complex with an outer protein shell, apoferritin and an hydrated ferric phosphate at its core)(Yehuda and Mostofky, 2010). People with iron deficiency anaemia have the usual anaemia symptoms but also symptoms such painless glossitis, angular stomatitis, brittle, koilonychia (spoon nails), dysplasia, pica (unusual dietary craving) and in children is associated with irritability, psychomotor and mental impairment (Hoffbrand, 2006).
Conversely, anaemia resulting from vitamin B12 and folate deficiencies (macrocytic anaemia) are less common than iron deficiency anaemia (microcytic hypochromic anaemia), this is a result of the body ability to store large amounts of vitamin B12 and folate (elderly people are normally the most affected). Both belong to a group called megaloblastic anaemias (abnormality-maturation of erythroblasts in the bone marrow and retardation of DNA synthesis) (Hoffbrand, 2006). Vitamin B12 and folate deficiencies are responsible for the majority of the cases of megaloblastic anaemia, for instance, in the case of Vitamin B12 deficiency the most common cause is a disorder called pernicious anaemia (where people do not produce the protein intrinsic factor responsible for the absorption of Vitamin B12), while in folate deficiency the cause is normally by insufficient iron intake (table 3) (Turgeon, 2005). Furthermore, since erythrocytes maturation process is also dependent of Vitamin B12 coenzymes and folates, the erythrocytes in megaloblastic anaemia show an abnormal nuclear maturation and disproportion between nuclear and cytoplasmic maturation, impairment of DNA synthesis (that will slow and delay nuclear replication and every step of maturation),and early synthesis of haemoglobin (Turgeon, 2005). Moreover, like in iron deficiency anaemia, deficiencies of vitamin B12 and folic acid can be originated by defects in absorption, transport or cell metabolism. In contrast to iron deficiency anaemia, the MCV in vitamin B12 and folic acid anaemia tends to increase before the haemoglobin levels decreases, the MCH values can vary but normally tend to increase and examinations of the blood film characteristic reveals macrocytic, ovalocytic erythrocytes of unequal size (anisocytosis) and different shapes (poikilocytosis) (Turgeon, 2005). Clinical chemistry assays are also a valuable tool in the case of pernicious anaemia (table 4). In this type of anaemia symptoms progresses gradually, it shows the same usual anaemia symptoms like in iron deficiency, however a variety of other symptoms such as dyspnoea, paraesthesia, sore tongue, weight loss, vague gastrointestinal disturbances and various neurological and psychiatric symptoms may follow (Hughes-Jones, 2004).
Blood is vital for life for its ability to deliver the necessary substances to every cell in the body, especially oxygen. Erythrocytes are the most numerous blood cells and their protein haemoglobin is the responsible for attach and carry oxygen molecules. Additionally, erythrocytes are made through a process involving specific steps and iron, vitamin B12, folic acid are among the necessary requirements in this process. If a deficiency in each of those three occurs the result is iron deficiency anaemia or vitamin B12 and folate anaemias. These anaemias are classified according to erythrocytes size as microcytic hypochromic anaemia (for iron deficiency) and macrocytic anaemia (vitamin B12/folic acid deficiencies). Furthermore, as they vary in a diversity of ways, this essay has highlighted some differences that are present such as haematological findings, clinical symptoms and responsible underlying causes for each of these deficiencies.
Table 1: Reference ranges of haemoglobin created by Maria Inacio with information from (Hughes-Jones, 2004)
Table 2: Conditions that can cause iron deficiency anaemia created by Maria Inacio with information from (Turgeon, 2005)
Table 3: Mechanisms and causes of vitamin B12 and folate deficiencies created by Maria Inacio with information from (Hughes-Jones, 2004)
Table 4: Valuable clinical chemistry assays in the diagnostic of pernicious anaemia. Created by Maria Inacio using information from Turgeon, M.L., (2005). Clinical Hematology: Theory and Procedures. 4th ed. Philadelphia: Linpicott Williams & Wilkins.
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Pallister, C.J., (2001). Biomedical Sciences Explained: Haematology.UK: Arnold.
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Turgeon, M.L., (2005). Clinical Hematology: Theory and Procedures. 4th ed. Philadelphia: Linpicott Williams & Wilkins.
Yehuda, S. and Mostofsky, D.I., (2010). Iron Deficiency and Overload: From Basic Biology to Clinical Medicine. USA: Human Press.