PART 2: Blood Disorders (Erythrocytes)

Anemia

• inability of the blood to carry enough oxygen to meet body needs

• may be due to low hemoglobin levels (commonly) or production of faulty hemoglobin

• may be classified depending on the cause:

  • production of insufficient or defective erythrocytes

  • blood loss or excessive erythrocyte breakdown (hemolysis)

Iron-Deficiency Anemia

• most common form of anemia

• RBC count is often normal, but the cells are small, pale and of variable size, and they contain less hemoglobin

• Causes:

  • Deficient intake

  • Unusually high iron requirements

  • Poor absorption (malabsorption) from the alimentary tract

1-2 mg

Daily iron requirement in men

3 mg

Daily iron requirement in women:

more

Children require ________ iron than adults to meet their growth requirements.

27

The amount of hemoglobin in each cell is regarded as below normal when the mean cell hemoglobin (MCH) is less than ___ pg/cell

9 g/100 mL

The anemia is regarded as severe when the hemoglobin (Hb) level is below ___________ blood.

vitamin b9

folic acid/folate

vitamin b12

cobalamin

Vitamin B12/folic acid deficiency anemia

• impairs erythrocyte maturation and abnormally large erythrocytes (megaloblasts) appear in the blood

• rate of DNA and RNA synthesis is reduced, delaying cell division, resulting in more time for cell enlargement

• Circulating cells are immature and larger than normal, and some are nucleated

• Mean cell volume (MCV) > 94fL

• Hemoglobin content of each cell is normal or raised.

• The cells are fragile and their lifespan is reduced to between 40 and 50 days.

• cause: Depressed production and early lysis

Pernicious anemia

• most common form of Vit B12 deficiency anemia

• Autoimmune disease in which autoantibodies destroy intrinsic factor (IF) and gastric parietal cells

• Females are affected more often than males

• frequently associated with other autoimmune disorders, particularly thyroid disease

• Common in the elderly

Vitamin B12

• widely available in animal-derived food products, including dairy products, meat, and eggs

• deficiency is rare except in strict vegans

• extensively stored in the liver

causes of vitamin B12 deficiency

• Gastrectomy (removal of all or part of the stomach)

• Chronic gastritis, malignant disease, and ionizing radiation

• Malabsorption (e.g. Crohn’s disease)

Megaloblastic anemia

• identical to that seen in vitamin B12 deficiency, but not associated with neurological damage

• caused by:

  • dietary deficiency (e.g. in infants if there is a delay in establishing a mixed diet, in alcoholism, in anorexia, and in pregnancy)

  • malabsorption from the jejunum caused by celiac disease, tropical sprue, or anticonvulsant drugs

  • Interference with folate metabolism by cytotoxic and anticonvulsant drugs

Aplastic (hypoplastic) anemia

• results from bone marrow failure

• RBC numbers are reduced. Since the bone marrow also produces leukocytes and platelets, leukopenia (low WBC count) and thrombocytopenia (low platelet count) are also likely

• Usually no cause is identified, but known causes include:

  • Drugs (e.g. cytotoxic therapy; rarely, aplastic anemia may occur as an adverse reaction to anti-inflammatory and anticonvulsant drugs and some antibiotics)

  • Ionizing radiation

  • Some chemicals (e.g. benzene and its derivatives)

  • Viral disease, including hepatitis

• presenting symptoms are usually infection, anemia, bleeding, and bruising

Pancytopenia

• all three cell types are low

• accompanied by anemia, diminished immunity and a tendency to bleed

• occasionally inherited

Hemolytic anemias

• occur when erythrocyte breakdown is increased

• takes place in the liver or spleen and the normal erythrocyte lifespan can be considerably shortened

• If the condition is relatively mild, there may be ongoing hemolysis without anemia. However, if the bone marrow cannot compensate, RBC numbers will fall and anemia results.

• additional symptoms such as jaundice or splenomegaly may be observed

Sickle Cell Anemia

• Congenital Hemolytic Anemia

• Genetic mutation → abnormal Hb → sickled RBCs

• Obstruction, ischemia, infarction; partial immunity to malaria

Thalassemia

• Congenital Hemolytic Anemia

• Inherited defect in hemoglobin production

• Ranges from mild to severe; marrow expansion; iron overload from transfusions

Hemolytic Disease of the Newborn

• Maternal antibodies destroy fetal RBCs (often Rh-related)

• Preventable with anti-Rh injection postpartum

Chemical / Drug-Induced

• Acquired Hemolytic Anemia

• Exposure to drugs, toxins, or chemicals

• No genetic link; RBC lysis from external agents

Autoimmune

• Acquired Hemolytic Anemia

• Autoantibodies target own RBC antigens

• Immune-mediated hemolysis

Transfusion Reaction

• Acquired Hemolytic Anemia

• Incompatible blood transfusion

• Sudden hemolysis; potential kidney damage from breakdown products

Polycythemia

abnormally high RBC count, which increases blood viscosity, slows blood flow and raises the risk of intravascular clotting, ischemia and infarction

Relative polycythemia

RBC count is abnormally high because the plasma volume is reduced (e.g. in burns)

True polycythemia

plasma volume is normal, but RBC count are high

Primary polycythemia

• Most cases are associated with a specific genetic mutation that interferes with erythropoietin control of erythrocyte numbers, leading to a condition called polycythemia vera.

• Patients present with itching, tiredness, headache, and sometimes complications from thrombosis. There is often liver and splenic enlargement.

• most common in the elderly (60 years old and above)

Secondary polycythemia

• This may be an expected compensatory response in hypoxic situations, such as living at altitude, heart failure or heavy smoking.

• It may also result from inappropriately high erythropoietin levels, seen in some kidney tumors, for example