Anaemia Flashcards
What is anaemia?
Anaemia is not a disease, but a term indicating insufficient haemoglobin to deliver oxygen to the cells. It is always a secondary phenomenon and it is essential to identify the underlying cause.
Anaemia can be defined as a haemoglobin (Hb) level of less than:
<130g/l (13g/dl) in adult males
<115g/l (11.5g/dl) in adult females
What are the symptoms of anaemia?
- Asymptomatic
- Tiredness/fatigue/ lassitude/ drowsiness
- Headache
- Weakness
- Light headedness /dizziness/vertigo
- Fainting
- Breathlessness on exertion
- Palpitations
- Worsening ischaemic symptoms e.g. Angina
- Intermittent claudication
- Menstrual disturbance
What are the signs of anaemia?
- Pallor
- Pale conjunctiva
- Pale palmar creases
- Tachycardia
- Postural hypotension
- Signs of congestive heart failure
- Murmur
- Brittle nails, koilonychia, brittle hair (Fe deficiency anaemia)
- Angular stomatitis, glossitis (Fe and vitamin B12 deficiency anaemias)
- Jaundice (haemolytic anaemia)
- Leg ulcers (sickle cell disease)
- Bone deformities (thalassaemia)
What do iron studies show?
Confirmatory investigations in the management of iron deficiency:
- Serum ferritin is a measure of the amount of stored iron in the body. Ferritin is the main protein that stores iron in the liver and the bone marrow
- Serum iron is a measure of the level of iron in the blood
- Transferrin is a blood protein that transports iron from the gut to the cells that use it. When iron stores are low, transferrin levels increase. Transferrin is low when there is too much iron in the body e.g. haemochromatosis.
Total Iron Binding Capacity (TIBC) - measures the amount of transferrin in relationship to the body’s need for iron
What are various types of anaemia and how are they detected?
Mean corpuscular volume (MCV) indicates the average RBC size (80-100fl). Microcytic anaemia = <80fl Normocytic anaemia = 80-100fl Macrocytic anaemia = >100fl)
The mean corpuscular haemoglobin (MCH) indicates the amount of haemoglobin present in the blood (27-31pg/cell).
Hypochromic anaemia = <27pg/cell
Normochromic anaemia = 27-31pg/cell
Hyperchromic anaemia = >31pg/cell
What are the causes of microcytic anaemia?
Chronic blood loss
Iron deficiency (Low iron stores, dietary lack of iron, malabsorption of iron)
Thalassaemia
Lead poisoning
What are the causes of normocytic anaemia?
Acute blood loss
Endocrine disease (hypopituitary, thyroid, adrenal)
Combined deficiency
Chronic disease
Sepsis
Tumour
Aplastic anaemia
What are the causes of macrocytic anaemia?
Megaloblastic anaemias (pernicious anaemia, nutritional deficiency anaemia of folic acid and vitamin B12)
Hereditary anaemias
Drugs
(Anticonvulsant, nitrofurantoin, alcohol excess -reduce folate absorption)
Liver disease
Hypothyroidism
Chemotherapy
Reticulocytosis*
What is ‘megaloblastic anaemia’?
Megaloblastic anaemia is the term used for anaemia due to a nutritional deficiency of either
vitamin B12 or folic acid, or malabsorption of B12 (pernicious anaemia).
Megaloblasts are unusually large nucleated erythroblasts. The cells are immature cells because of arrested development due to either B12 or folic acid (folate) deficiency. B12 and folate are essential cofactors in DNA synthesis. B12 and folate are only obtained from the diet or by supplement. Impairment in DNA synthesis delays nuclear maturation and cell division. The immature nucleated red cells are larger than normal RBCs. Therefore, the MCV is increased. Hence the term: macrocytic megaloblastic anaemia.
In high alcohol intake, the cells are macrocytic (high MCV), but anaemia is not usual. Excessive alcohol abuse can result in megaloblastic anaemia due to a toxic effect of alcohol on erythropoiesis and/or dietary folate deficiency
What is ‘pernicious anaemia’?
: Pernicious anaemia is the term used for a specific autoimmune disorder in which the gastric mucosa is atrophic and there is intrinsic factor deficiency. In the absence of intrinsic factor less than 1% of dietary B12 is absorbed. Vitamin B12 bound to intrinsic factor is absorbed in the last part of the small intestine. Parietal cell antibodies and/or intrinsic factor antibodies may be present. The patient may have other associated autoimmune disorders such as hypothyroidism. A patient with pernicious anaemia has a macrocytic megaloblastic anaemia.
What causes anaemia? (generally)
Anaemia occurs when either;
• there is a loss of RBCs due to bleeding
• the production of RBCs is decreased
•the destruction of RBCs is increased
- Blood loss**
- Acute haemorrhage e.g. trauma.
- Gradual, prolonged chronic bleeding resulting in iron deficiency e.g. gastrointestinal bleeding, menstrual bleeding - Nutrient deficiency or malabsorption**
- Iron deficiency, Vitamin B12 deficiency, Folate deficiency, Malnutrition - Chronic System Disease
- Anaemia of chronic disease, Kidney Failure, Liver Disease, Thyroid Disease - Immune Disease
- Autoimmune haemolytic anaemia, Transfusion reactions - ABO incompatibility - Infections
- CMV, Infectious mononucleosis, Malaria - Acquired bone marrow disease
- Aplastic anaemia, Leukaemia - Toxin exposure
- Drugs, Radiation, Alcohol - Genetic disorders
- Thalassaemia, Sickle Cell anaemia, G6PD deficiency - Microvascular Disease
- Haemolytic Uraemic Syndrome (HUS), Disseminated Intravascular Coagulation (DIC), Thrombotic thrombocytopenic purpura (TTP) - Other
- Pregnancy, Burns
What are the risk factors for iron deficiency anaemia?
• Female gender • Extremes of age • Lactation • Pregnancy • Poverty 20% of women of childbearing age in the world have iron deficiency anaemia
What type of anaemia is caused by blood loss, and when does this occur?
Overall, in acute haemorrhage, there is a rapid development of a normocytic normochromic anaemia with a reactive increase in reticulocytes (reticulocytosis) within 6 hours.
In chronic gradual blood loss, there is a gradual development of a microcytic hypochromic anaemia with or without a low serum ferritin due to low storage levels of iron. (Iron stores are used up replacing the lost red blood cells.) There is a reactive increase in the platelet count (thrombocytosis.)
Acute haemorrhage = normocytic normochromic anaemia
Acute haemorrhage can be due to trauma (wounds, major fractures, crush injuries), acute GI bleeding, rupture of an abdominal aortic aneurysm and surgery. Patients are at increased risk of haemorrhage if they are taking anticoagulant therapy e.g. warfarin or have an underlying defect in haemostasis.
Haematocrit (Hct) and Red Blood Count (RBC) will also fall and a reactive increase in the reticulocyte count (reticulocytosis) to increase the number of red cells will occur within 6 hours of onset of haemorrhage.
Gradual chronic loss = microcytic hypochromic anaemia
1. Gastrointestinal (GI) bleeding - e.g. drugs, cancer, gastric ulcer
•Melaena describes the passage of black tarry stools with an offensive smell, due to altered (digested) blood in the faeces. It implies a bleed at some point early in the GI tract, oesophagus, stomach or duodenum.
- Menstrual bleeding - Increased menstrual loss
• Menorrhagia is abnormally heavy and prolonged menstrual periods at regular intervals.
•Menometrorrhagia is prolonged or excessive bleeding occurring irregularly and more frequently than normal.)
Chronic blood loss leads to on-going iron loss and produces a microcytic hypochromic anaemia due to eventual iron deficiency. The red cells are small pale and hypochromic due to lack of iron. There is often an increase in platelet count (thrombocytosis) as a result of a reactive increase in bone marrow activity. In chronic GI loss, mass screening programmes on people over 55 years may detect Faecal Occult Blood (FOB positive) and this may be the first indication of more serious underlying GI pathology e.g. bowel cancer.
Be aware that microcytic/hypochromic erythrocytes may also be seen in the anaemia of chronic disease, in the thalassaemias and in the sideroblastic anaemias. In these anaemias iron stores are normal or increased e.g. serum ferritin is normal or increased.
In ulcerative colitis blood and mucous are passed resulting in iron deficiency. In iron deficiency anaemia, iron can be replaced with ferrous sulphate supplements (which incidentally also make the stools black. Not called melaena in this case, stools are not offensive.) Constipation is another side effect of ferrous sulphate.
When does anaemia due to nutrient deficiency occur?
Overall iron deficiency gives a microcytic picture, whereas folate and B12 give a macrocytic picture.
a) Nutritional deficiency of iron, B12, folate.
Nutritional deficiency of iron is the most common and widespread nutritional disorder in the world. Inadequate diet and poverty are the main factors. Meat is the main source of iron. Iron from vegetables is not as well as absorbed as that in meat. Vegetarians are at risk from iron deficiency unless supplements are taken. Vegans are particularly prone to Fe and B12 nutritional deficiency.
b) Malabsorption of iron and folate
In coeliac disease (gluten-sensitive enteropathy) combined iron and folate deficiency may occur. Folate deficiency leads to macrocytic cells. Iron deficiency leads to microcytic cells, giving mixed picture
In Crohn’s disease, anaemia is common and usually is a normocytic, normochromic anaemia of chronic disease. However, iron deficiency and/or folate deficiency may also coexist due to malabsorption. The size of cells will therefore be mixed and the picture could be microcytic, normocytic or macrocytic.
Other causes of malabsorption include achlorhydria, gastric surgery and small bowel resection.
c) Malabsorption of B12
What type of anaemia is caused by chronic disease?
The anaemia of chronic disease (ACD) is usually associated with a normal MCV (normocytic normochromic) and ferritin levels are normal or high, but serum iron is often low. Recent work suggests that hepcidin levels are high. Hepcidin is a regulatory protein, produced by the liver, which inhibits the export of iron into the blood. Iron remains trapped in storage sites in the form of ferritin.
