Anemia is defined as a reduced number of red blood cells or hemoglobin in the blood.  The purpose of the red blood cell is to deliver oxygen from the lungs to all of the cells of the body. Hemoglobin is the protein in red blood cells that carries the oxygen.  Anemias are categorized by the cause of the decrease in red blood cell number: decreased production, decreased survival, or increased loss of red cells.  Anemia may be normal in infants as the bone marrow is establishing adequate production of red cells or in menstruating females.  Anemia due to rapid loss of blood can be life-threatening.

 

Decreased production of red cells

• Physiologic anemia of infancy - Infants typically have a mildly low red blood cell count around the age of 6 to 8 weeks that progressively improves over several weeks.  This is related to the normal transition of an infant to producing red blood cells.
• Iron, folate or vitamin B12 deficiency - These vitamins and minerals are vital to the production of red blood cells.  Oral vitamin and iron supplements can correct this type of anemia.
• Transient erythroblastopenia of childhood (TEC) - This occurs when the immune system temporarily shuts down production of red blood cells.  The exact cause is not known.  TEC typically resolves without treatment, however in severe cases, blood transfusions may be necessary
• Red cell aplasia (ex.- during parvovirus B19 infection) - In healthy children, this problem self-corrects quickly and is usually not noticeable.  In children with other chronic illnesses, this may cause severe anemia requiring blood transfusions (such as in children with sickle cell disease).
• Anemia of chronic disease - The exact cause has not been identified but is problably related to multiple factors.  Often treating the primary disease will improve anemia.
• Kidney disease - This is caused by decreased production of erythropoietin, a hormone found in the kidneys that stimulates production of red blood cells.

Decreased survival of red cells

• Sickle cell anemia - Abnormally-shaped red blood cells are destroyed by the spleen.
• Thalassemia - Abnormal red blood cells are destroyed by the spleen.
• G6PD deficiency - Lack of this enzyme (G6PD) causes red cells to be destroyed prematurely.
• Hemolytic anemia - An over-active immune system destroys red blood cells.
• Disseminated intravascular coagulation - A life-threatening condition in which abnormal clotting damages red blood cells.
• Hemolytic-uremic syndrome - Red blood cells are damaged by bacterial toxins.
• Thrombotic thrombocytopenic purpura - Abnormal clotting damages red blood cells.
• Prosthetic heart valve - Red blood cells are damaged by the mechanical valve.
• Hypersplenism - An unusually large spleen traps too many red blood cells and platelets.

Increased loss of red cells (bleeding)

• Menstrual bleeding - Mild anemia in menstruating females is common.  Oral iron supplements may be necessary.  Heavy, irregular bleeding may require hormone therapy.
• Gastrointestinal bleeding - A large amount of blood can be lost in the gastrointestinal tract before being discovered.  Blood from the stomach may exit as black tarry stools or vomited material that looks like coffee-grounds.  Blood in the stool may appear black, dark red or bright red, depending on the location of the source of bleeding and the briskness of bleeding.
• Injury - Bleeding from an injury may be internal (causing a hematoma or bruise) or external.  Severe bleeding can be life-threatening.  The first treatment for bleeding is well-placed, direct pressure.  For dirty or large wounds, quickly clean the area to identify the bleeding source and push on the area (preferably with a clean cloth) and seek medical care!

Symptoms of anemia

Symptoms are typically more obvious when anemia develops quickly or is severe.

• Weakness
• Tiredness or decreased energy level
• Dizziness (especially when standing quickly after lying down or sitting)
• Fainting
• Rapid or pounding heartbeat
• Shortness of breath
• Decreased exercise tolerance
• Pale skin and lips

Treatment of anemia

Treatment depends on the cause.  See individual topic articles.