White blood cells (leukocytes) defend the body against infection. Normally, the body makes about 100 billion of these cells every day. They circulate in the blood and respond as needed to invading germs.

Types of White Blood Cells

White blood cells are a complex group. There are five types, divided into two categories:

  • Granulocytes
    • Basophils
    • Eosinophils
    • Neutrophils
  • Agranulocytes
    • Lymphocytes
    • Monocytes


The three types of granulocytes protect the body against infection by surrounding and destroying invading microorganisms. They are filled with tiny granules, each of which contains enzymes that digest these microorganisms.

Because they actually digest invading microorganisms, granulocytes are phagocytes (“phage-“ is a Latin root word meaning “eater”).


The class of leukocytes known as agranulocytes is usually referred to by type: monocytes or lymphocytes.

  • Monocytes. Dendritic cells and macrophages are the two types of monocytes. The primary activity of these white blood cells is to recognize and mark invading microorganisms.
  • Lymphocytes. B cells and T cells are types of lymphocytes. They attack microorganisms marked by monocytes. Lymphocytes can also be phagocytes, digesting invading microorganisms.

What Are White Blood Cell Disorders?

Disorders involving white blood cells generally increase or decrease the number of those cells in the blood or cause them to function improperly. These changes result in a variety of conditions. An inadequate number of white blood cells leaves the body open to infection.

Surprisingly, too many white blood cells can also lead to an increasing number of infections, because the increased level of white blood cells usually represents abnormal cells that crowd out healthy cells.

In white blood cell disorders, the number or function of white blood cells, or leukocytes, is disrupted. White blood cell disorders can have variety of causes, including:

  • Infections
  • Congenital disorders
  • Diminished bone marrow function
  • Drugs that destroy white blood cells

The number of white blood cells in healthy blood varies considerably. The count of white blood cells is generally considered a disorder when it decreases to less than 4,000 or increases to more than 11,000.

What Are the Different Types of White Blood Cell Disorders?

White blood cell disorders fall into three categories:

  • Too many white blood cells (leukocytosis)
  • Too few white blood cells (neutropenia)
  • White blood cells are not functioning properly


The most well-known disorder characterized by too many white blood cells is leukemia [Link to Leukemia condition page]. Leukemia is a cancer of the blood in which the bone marrow, which makes the body’s blood cells, makes immature, abnormal white blood cells. Unlike normal white blood cells, these abnormal cells don’t die. Instead, they divide and increase their numbers, crowding out healthy blood cells. Leukemia causes such problems as:

  • Anemia
  • Bruising easily
  • Fatigue
  • Frequent infections

Leukemia can sometimes appear and progress quickly. In this kind of leukemia, the abnormal cells don’t provide the protective function of normal cells. The leukemia cells reproduce quickly and cause acute symptoms.

As the number of leukemia cells rises, these cancerous cells crowd out normal cells. This disrupts normal functions of the blood (carrying oxygen and fighting disease). As a result, a child with leukemia can become very ill.

Aggressive leukemia can also spread to organs (metastasize), a condition that can be fatal.

There is also a slow form of leukemia (chronic) that is less dangerous. In this type of leukemia, the abnormal cells function nearly as well as normal white blood cells. However, because these abnormal cells don’t die, they do eventually begin to crowd out normal cells, including red blood cells. This can lead to anemia and other symptoms.


When a child has a very low amount of the white blood cells called neutrophils, he or she has neutropenia. The number of neutrophils can decrease for a variety of reasons. These include:

  • Chemotherapy
  • Leukemia (increasing numbers of abnormal white blood cells cause a decrease in the number of normal cells)
  • Lupus
  • Parasitic diseases
  • Viral infection
  • Nutritional deficiency
  • Medication
  • Congenital problem with bone marrow production of white blood cells

The main result of neutropenia is increased vulnerability to infections. Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) is a well-known disorder of this kind. HIV attacks white blood cells, decreasing the body’s ability to defend itself against infection. AIDS is a severe form of HIV infection.

What Are the Causes of White Blood Cell Disorders?


Diseases that cause leukocytosis include leukemia and acute infections. Leukemia increases the number of white blood cells tremendously. A normal white blood cell count is below 11,000. Counts of more than 100,000 are possible with leukemia.

Another cause of leukocytosis is bacterial or parasitic infection. When the body is fighting these infections, it will increase the number of white blood cells. This increase may overcome the infection. When it does not, antibiotics or other drugs can help the body defeat the infection. When the infection is over, the white blood cell count will probably decrease.


Some diseases can destroy white blood cells or damage the body’s ability to make them. Leukemia, which increases the overall number of white blood cells, actually decreases the number of healthy white blood cells. HIV/AIDS destroys white blood cells. Some parasites also attack white blood cells.

Chemotherapy, which is used to treat cancer and other diseases, can destroy white blood cells. As a result, a child being treated with chemotherapy is also at risk for developing serious infections.

What Are the Symptoms of White Blood Cell Disorders?

Because leukocytosis often results in a decrease in the number of healthy white blood cells, symptoms of leukocytosis and neutropenia can be similar. Common symptoms of these white blood cell disorders include:

  • Anemia
  • Bruising easily
  • Fatigue
  • Frequent infections

Neutropenia can also cause a dangerous condition called septic shock if a child who has neutropenia has a fever higher than 100.5 degrees. If your child has a fever, you should tell the doctor and follow his or her instructions.

How Are White Blood Cell Disorders Diagnosed?

White blood cell disorders such as leukemia that elevate your child’s white blood cell count cause changes in your child’s body that the doctor will recognize. These include:

  • Bruising
  • Enlarged liver
  • Enlarged lymph nodes
  • Enlarged spleen

If your child’s doctor suspects a white blood cell disorder, he or she will probably order blood tests, including a complete blood count (CBC). A CBC is an actual count of various kinds of cells in a set quantity of blood. An elevated or decreased count of white blood cells is a strong indicator of a white blood cell disorder.

A family history of white blood cell disorders is also an indicator that recognizable symptoms may be caused by one of these disorders.

How Are White Blood Cell Disorders Treated?

Treatments for white blood cell disorders depend on several factors, including:

  • The type of disorder
  • The extent of the disorder
  • Your child’s overall health
  • Your child’s response to treatment
  • Your preferences

Our treatments for your child’s white blood cell disorder may include:

  • Chemotherapy
  • Radiation
  • Antibiotics
  • Colony-stimulating factors (these increase the body’s production of blood cells)
  • Drugs to suppress the immune system

Stem cell transplantation may be useful for some types of severe white blood cell disorders, particularly those caused by bone marrow problems.

What Is the Long-Term Outlook for Children With White Blood Cell Disorders?

There are many causes and types of white blood cell disorders. Some disorders can be temporary, such as those caused by chemotherapy or infections. Others can last years, as with chronic leukemia and bone marrow problems.

The severity of white blood cell disorders varies, too. Aggressive leukemia can progress quickly and be life threatening. Leukocytosis caused by an infection may pose no threat and go away after the infection is defeated.

Only your child’s doctor can provide reliable information on the long-term outlook (prognosis) for your child.

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