From the Guidelines
Lymphocytosis, or a high lymphocyte count, is a condition that requires medical evaluation to determine its underlying cause, which can range from infections to autoimmune disorders or cancers, and treatment should focus on addressing the root cause rather than the lymphocytosis itself. This condition occurs when the blood has more than 3,000 lymphocytes per microliter, indicating that the body is fighting an infection or responding to another perceived threat. The causes of lymphocytosis can be varied, including viral infections like mononucleosis, influenza, or cytomegalovirus, certain bacterial infections, autoimmune disorders like rheumatoid arthritis, some cancers (especially lymphoma and leukemia), and stress responses 1.
Key Considerations
- Lymphocytosis is often a sign of the body's immune response to an infection or other stressor.
- The condition can be caused by a range of factors, including infections, autoimmune disorders, and cancers.
- Treatment should focus on addressing the underlying cause of the lymphocytosis rather than the condition itself.
- Medical evaluation, including additional tests such as blood tests, imaging studies, or possibly a lymph node biopsy, is necessary to determine the cause of lymphocytosis.
Diagnostic Approach
The diagnostic approach to lymphocytosis involves a stepwise evaluation, starting with a thorough medical history, physical examination, and laboratory tests to identify the underlying cause. According to the guidelines for the diagnosis and treatment of chronic lymphocytic leukemia, a high lymphocyte count can be a sign of this condition, but other causes must also be considered 1. The presence of lymphocytosis in bronchoalveolar lavage (BAL) fluid can also be an important diagnostic clue in certain cases, such as hypersensitivity pneumonitis 1.
Management
Management of lymphocytosis depends on the underlying cause. In some cases, such as mild, temporary elevations due to common infections, no specific treatment may be necessary, and the condition may resolve on its own. However, persistent lymphocytosis requires medical evaluation and treatment to address the underlying cause. It is essential to consult a healthcare provider for proper evaluation and management of lymphocytosis, rather than attempting to treat the condition on one's own.
From the Research
Significance of Lymphocytosis
Lymphocytosis, or a high lymphocyte count, can be an indicator of various conditions, including infections, immunological disorders, and malignant neoplasms.
- The clinical significance of lymphocytosis was investigated in a study published in 2018 2, which found that patients with infections had the highest high-fluorescence lymphocyte counts (HFLC), with most of those patients having dengue infection.
- Another study published in 2014 3 developed new thresholds for blood smear review by pathologists, finding that applying these thresholds could decrease laboratory workload without compromising patient care.
- A 2019 study 4 established absolute lymphocyte count thresholds for further review of peripheral blood lymphocytosis to screen for monoclonal B-cell populations in older adults, finding that the incidence of monoclonal B-cell populations increased with age.
Association with Immunopathological Mechanisms
Lymphocytosis has also been associated with different immunopathological mechanisms in systemic lupus erythematosus (SLE).
- A 2020 study 5 found that patients with SLE had elevated neutrophil counts and reduced lymphocyte counts, resulting in elevated neutrophil to lymphocyte ratios (NLR), which were associated with immune complex-driven disease and type I interferon activity.
- The study also found that high NLR was associated with neutrophil abnormalities, including enrichment for low-density granulocytes (LDGs) and increased levels of the serum neutrophil activation marker, calprotectin.
Prognostic Value
Elevated leukocyte counts, including lymphocytosis, have been found to be a harbinger of systemic inflammation, disease progression, and poor prognosis.
- A 2018 review 6 found that high but normal leukocyte counts at baseline predict increased cardiovascular and noncardiovascular mortality in older adults, and that elevated leukocyte count within the normal range may be a harbinger of increased systemic inflammation and subclinical disease.
- The review also found that leukocyte count correlates positively with genuine markers of systemic inflammation like C-reactive protein and interleukin 6, and that leukocyte counts have a stronger prognostic ability with regard to total and cardiovascular mortality than total cholesterol or low-density lipoproteins.