Erythorocyte Disorders Page!

(except hemophilia, which is covered on the hemostasis and coagulation page!)

Anything more than a cursory glance at erythrocyte disorders is outside of the realm of this course.  What you will really find here is simply a list of a few terms used to describe blood disorders and conditions.

Below is Some Terminology associated with Blood Disorders!

For the most part, I suspect that this terminology represents review for most of you.  This review is presented here as some of the terms used will crop up in future sections, notably in the material covering cardiovascular functions.

Polycythemia = too many RBC's

Polycythemia vera - eg. in bone marrow cancer = high RBC count, severely impaired circulation, imagine an 80% PCV; very viscous blood

Secondary polycythemia = secondary to decreased O₂ availability - seen in individuals living at high altitudes

Blood doping = an induced polycythemia in athletes; the athletes either infuse themselves with cells harvested earlier or treat themselves with erythropoietin.

Erythrocytopenia (means anemia - not used very commonly) = too few RBC's

Anemia - blood has an abnormally low O₂ carrying capacity

-the result is fatigue, pale colour, shortness of breath, chills

Hemorrhagic anemia - blood loss anemia

-acute anemia (eg. wound)

-persistent anemia - chronic ulcerative bleeding, hemorrhoids

Hemolytic anemia - RBC's rupture (lyse) prematurely, from Hb abnormalities, transfusion of mismatched blood, bacterial or parasitic infection

Aplastic anemia - destruction or inhibition of red bone marrow

-sometimes seen in cancer (although cancers can also induce polycythemia), or following exposure to toxins or ionizing radiation

-affects formation of all circulating cell types (thus, WBC's may also be decreased in number leading to infections)

-require transfusions & finally a bone marrow transplant

Iron Deficiency anemia - low Fe²⁺ intake, poor Fe²⁺ absorption or secondary to hemorrhagic anemia, undetected or hidden internal bleeding, profuse/prolonged menstruation

Athlete's anemia - illusory only - prolonged and vigorous exercise may increase the blood volume, giving the impression that iron concentration has been decreased.  Recall that the initial response to exercise and stress is to see a slight increase in hematocrit.

Pernicious anemia - Vit B₁₂ deficiency (sometimes in strict vegetarians) or deficiency of gastric "intrinsic factor", required for Vit B₁₂ absorption.

Kidney or liver disease-associated anemia; remember, these are the organs associated with erythropoietin production; erythropoietin production will fall when the function of either of these organs is impaired; likewise a reduction in erythropoietin production is associated with hypogonadism in males (remember, androgens stimulate erythropoietin production).

Hemoglobinopathy = abnormal Hb - usually associated with genetic disorders - eg. sickle cell anemia, thalassemias

Thalassemias - genetic defect in Hb molecule; thin, delicate RBC's (decreased RBC count - Mediterranean heritage)

Sickle cell anemia - This genetic defect in the Hb molecule results in formation of crescent (sickle) shaped RBC's.  This change in shape of the RBC results from amino acid substitutions in the beta chains of hemoglobin.  This genetic mutation, found on chromosome 11 (autosomal recessive), appears to have developed in African and Mediterannean regions where malaria is endemic (or epidemic).  The alteration of the amino acid sequence in the beta chains results in an "unusual stacking pattern" of the Hb molecules.  This atypical stacking pattern forces the RBC's into the sickle shape which is characteristic of the disease.  The sickle shape of the RBC's causes the RBC's, themselves, to stack.  These stacks of RBC's tend to occur where fine blood vessels bifurcate, often blocking blood flow and leading to hypoxia and extreme pain, particularly in joint regions.

Not only do polycythemias put undue strain on the heart, but paradoxically, so do anemias.  Anemias are associated with extreme thinning of the blood.  There may be a 50% reduction in the viscosity of the blood.  Associated with the hypoxia that develops and the reduced viscosity of the blood, there is an increase in central venous return to the heart.  The heart attempts to pump away all of the blood that returns to it!  Now that the blood is thinner, the blood is returning to the heart more rapidly.  The heart compensates by beating more quickly and more forcefully.  (we will discuss this phenomenon as "Frank Starling's Law of the Heart" in the cardiovascular section of the class!)  The heart is now pumping a greater volume of blood during a given time.  When an anemic person increases their physical activity level, their heart may not be able to pump their blood much faster.  The excess workload and the inability to increase cardiac output sufficiently during increased activity (eg. exercise) may lead to acute cardiac failure.