What is Granulocytosis? - Definition, Symptoms & Causes

Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

Granulocytosis is a potentially serious blood disorder that can be caused by several different conditions. This lesson will provide readers with information regarding the definition, causes, and symptoms of granulocytosis.

Too Much of a Good Thing

Dirk is a 39-year-old college professor who was recently diagnosed with leukemia, which is a cancer of the bone marrow (bone marrow produces blood in the body). Because of his leukemia and its treatments, Dirk often feels very tired, achy, and commonly has a fever.

Over the past couple of days, Dirk has started to feel particularly sick. He has felt extremely tired (more than usual), and he has been experiencing abnormal bleeding and has been sweating profusely during the night. Dirk had a feeling that these new symptoms were something other than his usual symptoms due to his cancer and treatment. Therefore, he decided to go see his doctor to see if these new symptoms might be the sign of something new. After performing several tests on Dirk, the doctor informed him that he had granulocytosis.

What is Granulocytosis?

Granulocytosis is a condition that results when there is an abundance of granulocytes in the blood. Granulocytes are a form of white blood cells (WBCs) that are produced by bone marrow and include eosinophils, neutrophils, and basophils. Granulocytes are part of a person's immune system, helping to defend the body against infections caused by bacteria, viruses, and other microorganisms.

When bacteria or viruses cause infection in the body, the body will respond by having the bone marrow create granulocytes to help destroy the infectious microorganisms. Therefore, it is normal for the number of granulocytes to increase during times of infection or inflammation. However, sometimes too many granulocytes will accumulate in the blood stream, which results in granulocytosis (some granulocytes in the blood is good, too many granulocytes in the blood is bad).

Granulocytes are white blood cells that include eosinophils, neutrophils, and basophils. This is a picture of a neutrophil.


One of the main causes of granulocytosis involves a type of cancer called chronic myelogenous leukemia. Chronic myelogenous leukemia (CML) is a cancer that affects bone marrow, causing the bone marrow to create too many WBCs/granulocytes. CML is most common in older men, especially those who have undergone radiation treatment for cancer. Granulocytosis often occurs in other forms of cancer that impact the bone marrow, which include polycythemia vera, primary myelofibrosis, and essential thrombocythemia.

Granulocytosis can also occur anytime there is wide-spread infection or inflammation in the body. Severe bacterial infections, kidney failure, severe burns, and heart attacks are examples of conditions that can result in an abnormally high number of granulocytes in the blood. It should be noted that although these conditions will cause the number of WBCs to increase as part of the normal immune response, they only occasionally develop into granulocytosis.

Chronic myelogenous leukemia is a type of cancer that causes bone marrow to produce more WBCs/granulocytes than usual, often resulting in granulocytosis.


Symptoms of granulocytosis include:

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