Lymphocytosis: Overview, Symptoms, Causes, Diagnosis and Treatments

what is lymphocytosis


Lymphocytosis is a condition in which the body has an excessively high quantity of lymphocytes, a subtype of white blood cells. Lymphocytes are immune system cells that are important for battling infections. Anyone may develop lymphocytosis as it is a rather common symptom. It is more prevalent in people who have been recently infected most commonly with viruses. It is also common in people with arthritis which is a chronic inflammatory disease. It may result in an incidence of an adverse reaction to a newly prescribed medication. Individuals with trauma or a life-threatening medical condition are at high risk of developing lymphocytosis. Moreover, the people whose spleens are surgically removed may also have a high lymphocyte count. Infections or other disorders may result in lymphocytosis, a condition that happens when the immune system is overloaded fighting them. Even if lymphocytosis cannot be prevented, it may be controlled by addressing the underlying cause.

Absolute lymphocytosis refers to a condition in which the lymphocyte count rises above the normal range, whereas relative lymphocytosis refers to a condition in which the proportion of lymphocytes to WBCs rises above the normal range. Lymphs absolute high is more common than relative lymphocytosis.

Lymphocytes’ normal range varies with age. It is dependent on the age and what ranges of lymphocytes are considered normal. An adult’s typical lymphocyte count ranges between 1,000-4,800 lymphocytes per µL of blood, depending on their age. For youngsters, the number of lymphocytes/µL blood ranges from 3,000-9,500.

When a doctor suspects lymphocytosis, a thorough blood count with a differential is ordered. In comparison to the baseline, this test shows an increase in WBCs and a higher-than-usual number of lymphocytes. To determine the cells, the doctor may prescribe further diagnostic blood tests, such as a flow cytometry test. Another kind of test that may be done to discover the underlying cause of lymphocytosis is a bone marrow biopsy. To figure out what is causing the lymphocytosis, doctors look at the medical history, medication list, present symptoms, and physical exam.

Lymphocytosis alerts the doctor that you are sick or have just recovered from an infection. Lymphocytosis is a common symptom of long-term viral infection. Lymphocytic leukemia, the most prevalent kind of leukemia in adults, has been shown to be one of the early signs and symptoms of several blood malignancies. Additional tests are often required to rule out other medical disorders and provide a definitive diagnosis of the lymphocytosis cause.

Lymphocytic treatment is condition-specific. While some elements are merely reactive or physiological in nature and may not need treatment (for example, stress or asplenia), others suggest the existence of a malignant or clonal process and may necessitate treatment.


Lymphocytosis, a condition marked by an elevated concentration of lymphocytes in the blood, can stem from diverse factors. The following are potential triggers:

  1. Infections: Elevated lymphocyte counts may result from viral infections such as mononucleosis (Epstein-Barr virus), cytomegalovirus, and pertussis.
  2. Bacterial Infections: Lymphocytosis can be induced by specific bacterial infections, including tuberculosis or Bordetella pertussis, which causes whooping cough.
  3. Chronic Inflammatory Disorders: Conditions like rheumatoid arthritis, lupus, and inflammatory bowel disease could contribute to heightened lymphocyte levels.
  4. Lymphoproliferative Disorders: Diseases like lymphoma or leukemia, characterized by abnormal lymphocyte increase, may lead to lymphocytosis.
  5. Medications: Some drugs, especially corticosteroids and specific anticonvulsants, may provoke lymphocytosis as a side effect.
  6. Stress or Physiological Response: Emotional or physical stress can temporarily elevate lymphocyte count as part of the body’s natural reaction.
  7. Hematologic Conditions: Certain blood disorders, such as hemolytic anemia or hemolytic reactions, might contribute to increased lymphocytes.
  8. Post-Splenectomy: The removal of the spleen (splenectomy) can result in an upsurge of lymphocytes in the bloodstream.

It’s essential to recognize that the specific cause of lymphocytosis can vary, and a comprehensive medical assessment is necessary for an accurate diagnosis.


A variety of underlying medical disorders might result in lymphocytosis. The presence of more lymphocytes in the blood indicates that the body is fighting an infection or another inflammatory disorder. A transient rise in lymphocyte count is a natural side effect of the body’s immune system when it is functioning appropriately.

One of the most common causes of increased lymphocytes is an infection that could be bacterial or viral. Cancer of the blood or lymphatic system is also considered to be associated with an increased count.

Acute stress and emergency medical difficulties may be accompanied by transient lymphocytosis.

Toxoplasma also causes lymphocytosis. Immunocompromised persons account for the bulk of instances of symptomatic toxoplasmosis. Lymphocytosis with aberrant cells is a hematologic feature of the disease, which in certain circumstances manifests as a mononucleosis-like illness.

Other diseased conditions that cause lymphocytosis include:

  • Chronic lymphocytic leukemia
  • Hepatitis
  • Hypothyroidism i.e. underactive thyroid
  • Cytomegalovirus (CMV) infection
  • Lymphoma
  • Congenital lymphocytosis
  • Syphilis
  • Tuberculosis
  • Mononucleosis
  • Whooping cough
  • Viral infections
  • Bacterial infections like Bordetella Pertussis and Bartonella henselae

Drug-induced lymphocytosis and systemic symptoms: Certain medicines might result in lymphocytosis. It is most likely due to cells being redistributed from lymphoid tissues into the peripheral circulation.


The diagnosis of lymphocytosis involves a systematic approach by healthcare professionals. Here are the general steps typically taken:

Medical History and Physical Examination

The doctor will review the patient’s medical history, looking for factors such as recent infections, exposure to toxins, or a history of chronic diseases. A physical examination may be conducted to check for signs of infection or other underlying conditions.

Complete Blood Count (CBC)

A CBC is a common blood test that provides information about the number and types of blood cells, including lymphocytes. An elevated lymphocyte count is indicative of lymphocytosis.

Peripheral Blood Smear

In some cases, a blood smear may be examined under a microscope to assess the size, shape, and characteristics of the lymphocytes.

Flow Cytometry

Flow cytometry is a more detailed analysis of blood cells. It can help identify specific types of lymphocytes and assess their proportions.

Bone Marrow Biopsy

If necessary, a bone marrow biopsy may be conducted to examine the cells in the bone marrow. This can help determine if there are abnormal lymphocytes or any signs of leukemia or lymphoma.

Additional Tests

Depending on the suspected cause, additional tests may be conducted. For example, tests for infectious agents, autoimmune markers, or imaging studies may be performed.

Specialized Testing for Underlying Conditions

If an underlying condition such as an autoimmune disorder or cancer is suspected, additional specialized tests may be ordered to confirm the diagnosis.

It’s important to note that the specific diagnostic process may vary based on individual cases and the suspected cause of lymphocytosis. A healthcare professional will tailor the diagnostic approach to the patient’s symptoms, medical history, and examination findings. Early and accurate diagnosis is crucial for determining the appropriate course of treatment.


The approach to treating lymphocytosis is contingent upon its underlying cause, emphasizing the importance of seeking personalized guidance from a healthcare professional. Nevertheless, here are some general directives based on potential causes:

Addressing Infections

  • Viral Infections: Specific antiviral medications may be prescribed to combat particular viruses.
  • Bacterial Infections: Antibiotics prove effective in treating bacterial infections.

Managing Inflammatory Disorders

  • Autoimmune Disorders: Immunosuppressive medications, like corticosteroids or disease-modifying antirheumatic drugs (DMARDs), may be recommended to diminish immune activity.
  • Inflammatory Bowel Disease: Medications targeting inflammation, such as anti-inflammatory drugs or immunomodulators, could be advised.

Treating Lymphoproliferative Disorders

  • Lymphoma or Leukemia: Treatment strategies may encompass chemotherapy, radiation therapy, immunotherapy, or stem cell transplantation, contingent upon the specific type and stage of the disease.

Adjusting Medications

  • If lymphocytosis is triggered by specific medications, healthcare providers might contemplate modifying dosages or transitioning to alternative medications.

Managing Stress-Related Lymphocytosis

  • Employing stress management techniques, encompassing relaxation exercises, meditation, and counseling, can be advantageous.

Addressing Hematologic Conditions

  • Hemolytic Anemia: Treatment centers on addressing the root cause and may involve medications or blood transfusions.

Monitoring Post-Splenectomy Lymphocytosis

  • In instances of lymphocytosis post-splenectomy, vigilant monitoring may suffice. If symptoms persist, additional medical management may be explored.

It is imperative to adhere to the healthcare provider’s counsel, attend regular follow-up appointments, and promptly communicate any alterations in symptoms or medication-related side effects. Self-medication or neglecting symptoms may lead to complications, underscoring the necessity to seek professional medical advice for an accurate diagnosis and an appropriate treatment plan.

When to see a doctor

A high lymphocyte count is often discovered as a consequence of testing performed for another purpose or to aid in the diagnosis of another ailment.

Inquire with the doctor about the significance of the test findings. When combined with the findings of other tests, a high lymphocyte count may help determine the cause of the sickness.

Specific blood tests may be necessary if lymphocytosis continues.

Immediately see your doctor if you have a persistent infection or if you are experiencing chronic or ongoing symptoms that are becoming worse over time. During a thorough medical examination, the primary care physician will be able to identify whether or not you have lymphocytosis.