WBCs develop from stem cells in the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow and are called leukocytes Leukocytes White blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes). White Myeloid Cells: Histology when circulating in the bloodstream. Lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology are 1 of the 5 subclasses of WBCs. Lymphocytosis is an increase in the number or proportion of the lymphocyte subclass of WBCs, often as a result of an immune response to infection (known as reactive lymphocytosis). Common presentations include fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy, and upper respiratory symptoms. Usually transient, lymphocytosis resolves on its own in most cases after resolution of the infection. In other situations, it may signal a lymphoproliferative disorder (known as clonal lymphocytosis). Diagnosis is based on peripheral blood smear Blood smear Myeloperoxidase Deficiency, flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure cytometry, and potentially, a bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow biopsy Biopsy Removal and pathologic examination of specimens from the living body. Ewing Sarcoma. Management depends on the underlying cause.
Last updated: Feb 7, 2023
Lymphocytosis refers to elevated levels of lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology. This elevation most often results from increased production.
Lymphocytosis may result from an increased production of lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology (most common) or several additional mechanisms.
The production of lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology may be increased because of:
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The pathophysiology depends on the underlying etiology. Increased production of lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology may be due to a clonal process or a reactive process.
The clinical presentation depends on the primary cause (i.e., infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease or lymphoproliferative disorders). Lymphocytosis can be an asymptomatic incidental finding.
Signs and symptoms may include:
Signs and symptoms may include:
The initial workup for lymphocytosis involves a comprehensive history and physical examination, CBC, and peripheral blood smear Blood smear Myeloperoxidase Deficiency. If the diagnosis is still uncertain, or if findings are worrisome for malignancy Malignancy Hemothorax, clonality should be established using flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure cytometry.
CBC findings associated with lymphocytosis include:
Peripheral blood smear Blood smear Myeloperoxidase Deficiency for lymphocyte morphology may show:
Peripheral blood smear showing a lymphocyte with hair-like cytoplasmic projections (known as “hairy cells”) in hairy cell leukemia
Image: “Peripheral blood smear” by Department of Pathology and Laboratory Medicine and Department of Hematology-Oncology, Tufts Medical Center, Tufts University Medical School, Washington Street 800, Boston, MA 02111, USA. License: CC BY 3.0Peripheral blood smear for a patient with infectious mononucleosis with atypical lymphocytes
Image: “Infectious Mononucleosis” by Ed Uthman, MD. License: CC BY 2.0Multiple peripheral blood smears showing lymphoblasts in ALL:
Background colors of sample images differ because of different magnifications being used in the images
Additional tests may be required based on the provisional diagnosis:
If lymphocytosis persists for ≥ 3 months and the cause is unclear, a further workup should be completed. This workup should include:
Management of lymphocytosis is related to the underlying etiology.