Approach to Lymphocytosis

Approach to Lymphocytosis

Peripheral blood smear. A population of mantle cells with a cleaved nucleus and paucity of cytoplasm

Lymphocytosis refers to an increase of peripheral blood lymphocytes, which for adults corresponds to >4000 lymphocytes/microL in most clinical laboratories. Lymphocytopenia refers to a decrease of peripheral blood lymphocytes, which generally corresponds to <1000 lymphocytes/microL in adults.

You can have a higher than normal lymphocyte count but have few, if any, symptoms. It usually occurs after an illness and is harmless and temporary. But it might represent something more serious, such as blood cancer or a chronic infection.

Your doctor might perform other tests to determine if your lymphocyte count is a cause for concern.

If your doctor determines that your lymphocyte count is high, the test result might be evidence of one of the following conditions:

  1. Infection (bacterial, viral, other)
  2. Cancer of the blood or lymphatic system
  3. An autoimmune disorder causing ongoing (chronic) inflammation

Specific causes of lymphocytosis include:

  • Acute lymphoblastic leukemia
  • Chronic lymphocytic leukemia
  • Lymphoma
  • Infectious mononucleosis
  • Cytomegalovirus (CMV) infection
  • Hepatitis A
  • Hepatitis B
  • Hepatitis C
  • HIV/AIDS
  • Other viral infections
  • Syphilis
  • Tuberculosis
  • Whooping cough
  • Hypothyroidism (underactive thyroid)
References:

Tracy I. George, MD. Diagnostic Approach to Lymphocytosis https://www.hematology.org/Thehematologist/Ask/4507.aspx

Lymphocytosis (high lymphocyte count). https://www.mayoclinic.org/symptoms/lymphocytosis/basics/causes/sym-20050660

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