A condition where there is a lower than normal amount of hemoglobin in the blood and red blood cell production is reduced. Other forms of anemia are caused by malfunctioning red blood cells, such as in sickle cell anemia. Often causes pallor and fatigue.

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From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.

Anemia describes the state where the red blood cell count, or the amount of hemoglobin in each cell, is pathologically low. This prevents sufficient oxygen from reaching the tissue of the body. Anemia is always symptomatic of some other problem -- not a disease in and of itself. Diagnosis and treatment should be conducted by physician as there are too many factors for the layman to consider. Figures for the United States suggest that 2-10% of people suffer an anemic condition. Most other nations suffer higher numbers.

Signs and symptoms of anemia vary widely (and while some are caused by and others are causes of -- each of these can be used diagnostically by a physician). Symptoms can be extremely painful or completely unnoticable. These signs include: cardiac abnormalities, chest pain, cramps in the lower leg, depression, faintness, fatigue, headache, impaired cognitive function, jaundice, low blood pressure, pallor, rapid respiration, sweating, thirst, vertigo, weakness and weight loss. Symptoms may lead a patient to seek medical counsel resulting in diagnosis, but often mild anemia is discovered through routine blood tests. Further testing is typically performed to determine causes.

There are three broad causes of anemia: blood loss, compromised red blood cell production and abnormal rate of red blood cell destruction. Anemia-inducing blood loss can be caused by: childbirth, injury or surgery or by more chronic situations including: gastro-intestinal ulcers (causing black and tarry stools or rectal bleeding) or cancers, hemorrhoids, menstrual bleeding, nosebleeds or tumors or the kidney or bladder. Compromised red blood cell production can be caused by deficiency of dietary elements including: folic acid, iron, vitimin B12 or vitimin C or other factors such as: arthritis, bone marrow dysfunction, chemo/radio-therapy, chronic disease/infection, leukemia, lymphoma, metastatic cancer, myelodysplasia or myelofibrosis. Abnormal red blood cell destruction can also be caused by a number of conditions, including: autoimmune dysfunction, enlarged spleen, G6PD deficiency, hereditary elliptocytosis, hemoglobin C disease, hemoglobin E disease, hemoglobin S-C disease, hereditary spherocytosis, mechanical damage, paroxysmal nocturnal hemoglobinuria, sickle cell disease or thalassemia. Also, water-weight gain in pregnant women can dilute the blood sufficiently to cause anemia.

As with the symptoms and severity, the treatments of anemia range from very minor (solar therapy) to substantial (hysterectomy). These include: erythropoietin hormone therapy, hysterectomy, infection treatment, nutritional supplements and transfusion of blood.

GTKY: my daughter was born slightly anemic -- clearly jaundiced. The advice given by our midwives was to bathe her in sunlight for two days and see a physician if it didn't resolve. We did. It did. We took her to the doc anyway, just to discuss it.

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The Merck Manuals Online: http://www.merck.com/mmhe/sec14/ch172/ch172a.html
the Mayo Clinic: http://www.mayoclinic.com/health/anemia/DS00321/DSECTION=3
Anemia Causes and Treatment, Ernest H. Rosenbaum, MD, Cancer Supportive Care Programs: http://www.cancersupportivecare.com/anemiacause.html
eMedicineHealth: http://www.emedicinehealth.com/anemia/article_em.htm

Anaemia is a sign of disease rather than a diagnosis in itself. The basic definition of anaemia is of a decrease in the level of haemoglobin (Hb) in the blood below a set reference range for the age and sex of the patient.

cord blood  –  13.5-20.5 Hb g/dL first day of life  –  15.0-23.5 Hb g/dL child, 6mths-6yrs  –  11.0-14.5 Hb g/dL child, 6-14yrs  –  12.0-15.5 Hb g/dL adult males  –  13.0-17.0 Hb g/dL adult females  –  12.0-15.5 Hb g/dL pregnant females  –  11.0-14.0 Hb g/dL

Mechanisms of Anaemia

In healthy adults, the release of new red blood cells (RBC) into the circulation and the removal of senescent red blood cells by macrophages should have a steady-state equilibrium. Thus, anaemia occurs if there is:

• a decrease in the life span of red blood cells, due to either congenital or acquired defects.
• an impairment in the production of red blood cells, either due to insufficient or ineffective erythropoiesis
• pooling or destruction of red blood cells in an enlarged spleen
• increased plasma volume, for example due to pregnancy or splenomegaly
• a loss of a significant amount (over 750mL) of blood

Morphological Classification of Anaemia

There are three major classes of anaemia. These are based on the mean corpuscular volume (MCV), which is the volume of the average red blood cell; and the appearance of the red blood cells in a stained blood smear under the microscope.

Hypochromic, microcytic with a low MCV - This category describes anaemias where the RBCs are smaller than usual (microcytic) and are lighter in colour than they should be (hypochromic). e.g., iron deficiency anaemia

Normochromic, normocytic with a normal MCV – This category describes anaemias where the RBCs are microscopically normal. e.g., acute blood loss

Macrocytic with a high MCV – This category describes anaemias where the RBCs are larger than expected. e.g., Vitamin B12 or folate deficiency

There are also a large number of abnormal cell morphologies that can be seen in a stained blood smear; these include sickle cells, target cells, spherocytes, microspherocytes and Howell-Jolly bodies.

Signs and Symptoms

Patients with a significant anaemia can be asymptomatic, as the slow lowering of haemoglobin levels allows the body to compensate. This adaptive response is achieved via the action of 2,3-diphosphoglycerate (2,3-DPG), which lowers the O₂ affinity of haemoglobin, causing a shift in the oxygen dissociation curve to the right. This means that oxygen is more readily given up to the tissues by blood.

It is important to realise that because anaemia is often the result of a disease process, the symptoms that a patient complains of may be caused by the underlying disease rather than the anaemia. Symptoms that are due to anaemia are often quite mild until the haemoglobin concentration drops below 7-8 Hb g/dL.

When the haemoglobin concentration drops below 7-8 Hb g/dL, the cardiovascular system itself has to make adaptive changes in order to maintain the supply of oxygen to the body. It does this by increasing the stroke volume of the heart and also by increasing the heart rate. This results in an increase of the cardiac output at rest.

There are two mechanisms that underlie the many symptoms and signs of anaemia:

1. decreased delivery of oxygen to body tissues which results in organ dysfunction.
2. adaptive changes made by the body to increase the delivery of oxygen to the tissues.

Symptoms that patients may complain of are fatigue, breathlessness, headache, faintness, visual disturbances, anorexia, nausea, bowel disturbances, menstrual disturbances, loss of libido, chest pain (angina), pain in legs after a period of walking (intermittent claudication) and palpitations.

Signs include pallor and tachycardia, and in extreme cases, wide pulse pressure, haemic murmurs and signs of congestive cardiac failure. There may also be disease specific signs, such as koilonychia for iron deficiency anaemia or jaundice due to haemolytic anaemia.

Investigations

Full Blood Count (FBC) – simple blood test to measure haemoglobin concentration, red cell and reticulocyte numbers and various other parameters of red blood cells, as well as a count of white blood cells and platelets.

Blood Film – examines the morphology of the blood cells.

Bone Marrow Aspirate – further investigates any unexplained abnormalities discovered in the FBC, and looks at the morphology of developing haemopoietic cells.

Further investigative procedures are determined by the type of anaemia present, as is the type of treatment that the patient is given.

Types of Anaemia

(This is by no means an exhaustive list; there are many rare causes of anaemia that I haven't put in here for fear of not being able to see the woods for the trees.)

Microcytic iron deficiency anaemia anaemia of chronic disease sideroblastic anaemia thalassaemia trait (α or β) lead poisoning

Normocytic anaemia of chronic disease aplastic anaemia haemolytic anaemias, e.g., sickle cell anaemia, haemolytic disease of the newborn (HDN), malaria

Macrocytic megaloblastic anaemia, due to vitamin B12 deficiency (pernicious anaemia), folate deficiency, or other causes of defective DNA synthesis aplastic anaemia alcoholism liver disease drug treatment with cytotoxic agents e.g., azathioprine

References

• Hughes-Jones N C, Wickramasinghe S N, Hatton C, 2004, Lecture Notes On: Haematology, 7th edition, Blackwell Publishing, 18-20
• Kumar P, Clark M, 2002, Clinical Medicine, 5th edition, WB Saunders, 410-411