Lymphocytosis
Lymphocytosis is defined as an abnormal increase in lymphocytes, a type of white blood cell essential for fighting infections, in the bloodstream. An absolute lymphocyte count (ALC) exceeding 4,000 lymphocytes per microliter of blood in adults indicates lymphocytosis, although children may have higher normal levels. This condition can arise from a variety of underlying medical issues, with viral and bacterial infections such as mononucleosis and influenza being the most common causes. Lymphocytosis itself is not a disease but a sign of other health problems, which may include hematological malignancies like leukemia and lymphoma.
Symptoms associated with lymphocytosis may include sore throat, fever, and fatigue, but it often goes unnoticed and is discovered during routine blood tests. A complete blood count is typically used for diagnosis, and further tests may evaluate different lymphocyte subsets to identify potential underlying conditions. Treatment focuses on addressing the root cause of lymphocytosis, and while it can resolve on its own, some cases may necessitate medical intervention. Understanding lymphocytosis and its implications can aid in recognizing potential health issues and seeking appropriate care.
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Subject Terms
Lymphocytosis
ALSO KNOWN AS: Raised lymphocyte count, high lymphocyte count
RELATED CONDITIONS: Lymph symptoms, absolute lymphocytosis, hematological malignancy, lymphoma, leukemia, lymphoproliferative disorders
DEFINITION: Lymphocytosis is an abnormal excess of lymphocytes in the blood. Lymphocytes are a type of white blood cell that help fight infections. A healthy adult has an absolute lymphocyte count (ALC) of 1,300 to 4,000 per microliter of blood. ALC over 4,000 indicates lymphocytosis. However, this number may be higher in children up to six years of age, as their ALC is significantly higher, up to 8,000 lymphocytes per microliter of blood.
Risk factors: More than thirty medical conditions may underlie lymphocytosis. The most common causes include viral and bacterial infections, such as mononucleosis (glandular fever), influenza, pertussis (whooping cough), or tuberculosis. Malignant blood diseases, such as chronic lymphocytic leukemia, follicular lymphoma, hairy cell leukemia, and leukopenia, may also cause lymphocytosis.
Etiology and the disease process: Lymphocytosis indicates an underlying problem, but it is not a disease in itself. The lymph nodes are the most commonly affected organs. Transient stress lymphocytosis may also occur after trauma or extensive psychological or physical stress, and it typically resolves within two days of diagnosis. Transient stress lymphocytosis may be in part mediated by modulation of catecholamine and steroid hormones and cell adhesion molecules.
Incidence: Lymphocytosis is common and occurs in most people throughout life, usually associated with viral infections. Rarely, monoclonal B-cell lymphocytosis (MBL) may become lymphocytic leukemia (CLL).
Symptoms: Symptoms of lymphocytosis may include sore throat, fever, and fatigue. However, lymphocytosis typically causes no symptoms and is often discovered incidentally via a routine blood test.
Screening and diagnosis: A complete blood count will identify lymphocytosis. Further investigation assesses major lymphocyte subsets, such as T cells, B cells, and natural killer cells. The subgroups of T cells are CD4 T cells (helper cells) and CD8 T cells (cytotoxic cells). In a healthy person, approximately 75 percent of lymphocytes are T cells, with a 2:1 ratio of CD4 to CD8, and about equal proportions of the remaining cells are B cells and natural killer cells. A marked increase in lymphocytes may indicate a serious condition, such as chronic lymphocytic leukemia, large granular lymphocytic leukemia, acute lymphoblastic leukemia, and non-Hodgkin's lymphoma. Many types of blood cancer are often identified after diagnosing lymphocytosis.
Treatment and therapy: For the best therapy, addressing the underlying issue that caused lymphocytosis is necessary. If a malignant blood disease is detected, cancer treatment may be needed.
Prognosis, prevention, and outcomes: Depending on the cause of lymphocytosis, it may spontaneously resolve or require medical intervention to relieve its symptoms.
Bibliography
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Hamad, Hussein, and Ankit Mangla. "Lymphocytosis." National Library of Medicine, 17 July 2023, www.ncbi.nlm.nih.gov/books/NBK549819. Accessed 20 June 2024.
Hoffman, Ronald, et al. Hematology: Basic Principles and Practice. 8th ed. Elsevier, 2023.
"Lymphocytosis." Cleveland Clinic, 16 May 2022, my.clevelandclinic.org/health/diseases/17751-lymphocytosis. Accessed 20 June 2024.
Rodak, Bernadette F., et al. Hematology: Clinical Principles and Applications. 6th ed. Elsevier, 2020.
Schmaier, Alvin H., and Hillard M. Lazarus. Concise Guide to Hematology. 2nd ed. Wiley, 2019.