D.2.4. Anemia and Polycythemia

A. Anemia:

An anemia is a lack of RBC’s (=erythrocytes).

There are essentially three reasons why an anemia occurs:
a. Loss of RBC’s
b. A deficiency in the RBC’s
c. A too slow or no production of RBC’s

B. Blood Loss Anemia: top?
Acute bleeding: In that situation, plasma is replaced in 1-3 days while RBC’s are replaced (by the bone marrow) in 3-4 weeks. So, the hematocrit will first quickly decrease and then slowly recover.

Chronic bleeding: This will often cause a lack of iron. Then the hemoglobin concentration in the RBC will decrease => this will cause microcytic (small) hypochromic (pale) anemia.

Chronic bleeding is often caused by a small seeping wound in the gastrointestinal system (ulcer) or, in females, due to excessive menstruations.

C. Deficient Erythrocytes: top?
We will discuss the following diseases: a. Aplastic anemia (= bone marrow aplasia) b. Megaloblastic anemia c. Hemolytic anemia
Aplastic anemia:
It really means that there is not enough bone marrow to produce RBC’s. (aplastic = abnormal or not developed)
This can be caused by excessive radiation, X-ray treatments, drugs, or exposure to radioactivity (such as during a nuclear disaster).
Megaloblastic anemia:
Caused by a deficiency in intrinsic factor, or vitamin B12 (= pernicious anaemia) and/or folic acid.
These defects cause slow RBC production => too large, odd shaped cells => megaloblasts => fragile, and therefore a short life span.
Hemolytic anemia:
Abnormal RBC (many hereditary), which are fragile, and have a short life span. (hemolysis = destruction of RBC’s).

There are several types of hemolytic anemia’s:
a. Hereditary spherocytosis
b. Sickle Cell anemia
c. Erythroblastosis Foetalis
d. Thalasaemias.
Hereditary spherocytosis:
In this disease, the erythrocytes are small and spherical. Not at all good for gas exchange or flexibility while flowing in the capillaries!

Sickle Cell Anemia:
In this disease (caused by an abnormal HbS molecule), the Hb inside the erythrocytes may crystallize and force the RBC’s to develop a ‘sickle’ shape. Again not very good for flexibility etc.
Erythroblastosis Foetalis:
This happens when the fetus is Rhesus positive (Rh+) while the mother is Rhesus negative (Rh-). Then the antibodies from the mother will attach and destroy the erythrocytes of the fetus! (see for more: D.6. Blood Types).
Hereditary diseases (quite common in the Middle East) where the beta-globuline chains in the HB molecule are abnormal or deficient.

D. Other anemia classifications: top?
Unfortunately, other medical disciplines may also use a different classification of these anemia’s, such as this one:
a. Microcytic anemia (low MCV) (MCV= Mean Cellular Volume)
b. Normocytic anemia (normal MCV)
c. Macrocytic anemia (high MCV)

E. Polycythemia: top?
This is the opposite of an anemia. In polycythemia, there are too much RBC’s!
Therefore, the hematocrit (Ht) has increased (for example, from 45% to 60% or 70%!
Physiological Polycythemia:
This is a normal response of the body (and the bone marrow) when one is living at a high altitude for example. (For more, see *Nice to know*)
Secondary Polycythemia:
This is a response of the body when there is a cardiac or a pulmonary problem (then, due to hypoxia, more RBC’s are created).
Polycythemia Vera:
(Vera = true). Thus, a true or a “real” polycythemia that is caused by a cancer in the bone marrow. Then, the Ht can increase to 80%! (Very dangerous! See panel G).

F. Doping: top?
When someone, usually an athlete, wants to perform better than the competition. More RBC’s can help a lot. But how do you make more RBC’s?

There are several ways in which you can increase artificially your RBC’s:
a. Auto transfusion
b. EPO
c. High Altitude
Auto transfusion:
About one month before the competition, you puncture and bleed a vein and store one litre of your blood in the fridge. The body will detect this loss of blood and make new RBC’s in the following weeks.

A few days before the competition, you take out the blood in the fridge and infuse it back into your circulation. Great; you now have more RBC’s then the competition!
(The cyclist Lance Armstrong and his colleagues were caught doing this for many years! Shame!!)

EPO is shorthand for artifical erythropoietin. This hormone is important for patients that do not make enough erythropoietin; kidney patients for example

But in competition, you can also inject EPO in a normal person to increase the RBC’s to higher levels. This is for example very popular in sports as cycling (Tour de France!), marathon etc where the body has to work very hard and where you want to WIN!
Another way to artificially increase your RBC is to live for some time at high altitude. So, about a month before the competition, move to Mexico, Peru or Nepal and allow your bone marrow to produce more RBC’s. A few days before the contest, fly back to the games and you win the competition!

G. Problems caused by anaemia and by polycythemia: top?
In both cases (to much or too little erythrocytes) the problem is the same; the heart has to work much harder.

In the case of anaemia, the heart will pump harder to circulate the blood, with its smaller amount of RBC’s and haemoglobin, to transport more oxygen to the working tissues.
In the case of polycythemia, the viscosity of the blood has increased. Therefore, it is more difficult for the blood to flow through the arteries, veins and capillaries.

Therefore, the blood pressure has to increase to push the blood through the circulation and this means that the heart must work harder.

Therefore, the symptoms in both anaemia and polycythemia are similar:
a. increase in heart rate (tachycardia)
b. stronger heart contractions (palpitations)
c. if chronic => cardiomegaly (big heart)

Finally; heart failure. Possibly death!

H. *Nice to know* top?
As stated in E.3 (Erythrocyte Production), people living at high altitude, such as in the Andes Mountains (South America), produce more RBC’s to compensate for the lower oxygen content in the atmosphere: Polycythemia. This is also why they often have red cheeks!
However, this is not necessarily a good thing as a higher hematocrit may also cause a higher chance of coagulations and a risk factor for stroke.

Interestingly enough, the people living in Tibet, also at a high altitude, do not increase their RBC’s and therefore do not have an increased hematocrit. They compensate the lack of oxygen in the atmosphere by increasing their lung ventilation!

In fact, the difference in response between the Andes people and those living in Tibet was the subject of research that led to a Nobel Prize in Physiology in 2019! (see: Prabhakar NR).

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D.2.4. Anemia and Polycythemia

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