Leukemia – Tissue and Systems

This article describes the systems involved with the disease of leukemia.  Leukemia is among the top ten causes of cancer related death for both men and women in the United States.  Leukemia is also the 9th most common cause of cancer among males in the United States. There are many different kinds of leukemia and this term is really a broad heading under which there are at least 50 different subtypes.  Given the broad variety of this disease, complete description of all of these could easily fill several textbooks.  The main points to be emphasized will be the common bodily systems that all of these diseases involve in order to better understand the symptoms that might be caused by this disease.  Although there are many kinds of leukemias, there are common and related symptoms to most of these.

In order to understand the main dysfunction of leukemia it is necessary to briefly review the normal function of bone marrow and blood cell production.  The production of different kinds of blood cells by the bone marrow is referred to as hematopoiesis.  During early stages of development, blood cells are made in the yolk sac, liver and spleen.  Eventually, this role is taken over primarily by the bone marrow.  In addition to providing strength, stability, and levers for movement; our bones contain the manufacturing station for the blood cells essential for life.

Within the center of the bones, the marrow contains specialized cells that are capable of generating several different kinds of blood cells.  This property is known as pluripotency.  These cells are called stem cells.  The stem cells within the bone marrow give rise to three main categories of blood cells:

  • White blood cells (B & T Cells, Natural Killer Cells, Monocytes, Eosinophils, Neutrophils, Basophils, Mast Cells)
  • Red blood cells (Erythrocytes)
  • Platelets

Each of these cells performs several functions.  Leukemia involves over-production of immature blood cells and a subsequent decrease in the other kinds of blood cells.  Understanding the function of these different types of cells will help explain the symptoms of leukemia.

Platelets: Platelets are derived from bone marrow stem cells that form myeloid daughter cells.  These myeloid daughter cells make megakaryocytes.  Each megakaryocyte makes many platelets.  We normally have about 150-500,000 platelets per microliter.  The primary function of platelets is to assist with stopping bleeding.  Having too few platelets is known as thrombocytopenia.  Having excessive platelets is known as thrombocytosis.  The platelets form little “plugs” at sites of bleeding to help stop hemorrhage.  The platelets have little packets of chemicals within each to help recruit more clotting at an area of injury.

Platelets may be present in adequate numbers but not function properly.  Several diseases such as kidney failure make the platelets not function properly.  One of the most common reasons for dysfunctional platelets is therapy with medications like aspirin.  With inadequate platelets, there is easy bruising and bleeding.  Pin-point little bruises or bleeding spots are known as petechiae.  Some with very low platelets will bleed into joins such as the knee.  This is referred to as hemarthrosis.  Another simpler sign of problematic platelets is taking a long time to clot a small cut.  Some people commonly refer to this as being a “free bleeder.”

Red blood cells: Red blood cells (also known as erythrocytes) perform the primary function of transporting oxygen in the blood to the entire body.  Red blood cells last about 3-4 months and older cells are recycled by the spleen.  Red blood cells contain the protein hemoglobin which uses iron to help transfer oxygen.  Oxygen is picked up in the lungs and is delivered when the red blood cells pass through capillaries in various organs and parts of the body.  The average person has about 5,000,000 red blood cells per microliter.  This count is more commonly expressed as the percentage of red blood cells in whole blood known as hematocrit.  The normal percentage is about 40%.  When red blood cells are present in excess, the excessive thickness of the blood makes blood circulation more difficult.  When red blood cell numbers are deficient this is known as anemia.  Anemia causes a pale appearance to the skin.  Anemia causes a feeling of tiredness or easy fatigue.  This is because of inadequate oxygen transport.

White blood cells:  As described above there are many different kinds of white blood cells.  These function collectively as the security guards of the body.  There are two functional types of white blood cells.  The innate immune system includes cells such as neutrophils and monocytes.  These cells have the ability to react to and kill a foreign invader such as bacteria upon contact.  They do not have to have had prior contact with the invader or have a memory of them.  The “memory” portion of the immune system involves white blood cells called lymphocytes.  Lymphocytes produce antibodies which are function like tags or markers to identify foreigners.  Lymphocytes subdivide into B-cells, T-cells and also natural killer cells.  These cells have the unique ability to sample or read the markings on the outside of cells to see if they are infected with a virus or do not belong.  A decrease in the number or function of white blood cells causes problems with healing, cancer and invasion of foreign intruders such as bacteria or viruses more common.  White blood cells form through a variety of stages from the stem cells to their final assigned roles.

Leukemia involves abnormal production of immature white blood cells.  Not only does this impair the function of white blood cells, it crowds out the other types of blood cells explaining the broad and serious symptoms that might occur.  Because there are so many different types of white blood cells and stages of development, it is easy to see how there could be many different varieties of leukemia.

REFERENCES:

  1. www.nlm.nih.gov/medlineplus/acutelymphocyticleukemia.html
  2. www.cancer.gov/cancertopics/types/leukemia
  3. Abeloff, M.D. (2008). Abeloff: Abeloff’sClinical  Oncology, 4th ed. Chapter 101. Philadelphia, PA: Churchill Livingstone – Elsevier
  4. Goldman, L ;  Schafer A.I.  (2011). Goldman: Goldman’s Cecil Medicine, 24th ed. Chapter 189, 190. New York, NY: Elsevier Saunders
  5. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.