17751 Lymphocytosis

Overview

Lymphocytosis means you have a higher-than-normal number of lymphocytes in your blood. Lymphocytes are a type of white blood cell that helps your body fight infections. This finding is not a disease itself, but a signal that something else is going on, such as an infection or an immune response.

Yes, lymphocytosis is fairly common. It is often a temporary finding in children and adults during or after an infection.

Lymphocytosis can affect anyone, but it is especially common in children and young adults with viral infections. It can also be seen in older adults, sometimes as a sign of a chronic blood condition, but this is much less common.

Symptoms

Common symptoms

• No symptoms at all – lymphocytosis is often found by chance.
• Symptoms of the underlying infection, such as fever, sore throat, cough, or tiredness.
• Swollen lymph nodes (glands in the neck, armpits, or groin).

Symptoms in children

• Fever, runny nose, and cough from common viral infections.
• Tiredness or irritability.
• Loss of appetite or mild stomach upset – these are often just signs of the infection.

Symptoms in older adults

• Sometimes no symptoms at all.
• Fatigue, weakness, or feeling generally unwell.
• Lymph node swelling, easy bruising, or night sweats – if these occur, they should be checked.
• Weight loss without trying.

Causes

Main causes

• Viral infections, such as EBV (glandular fever), cytomegalovirus, flu, or COVID-19.
• Bacterial infections, like whooping cough (pertussis).
• Stress from injury, illness, or surgery.
• Autoimmune conditions, like an overactive immune response.
• Medications, including some antiseizure drugs or steroids (a doctor can advise).
• Blood disorders, such as chronic lymphocytic leukemia (CLL) or lymphoma – these are rare but serious.

Risk factors

• Being a child or young adult, as infections are more common.
• Having a recent viral or bacterial infection.
• Weakened immune system from another condition.
• Age – older adults are more at risk of chronic forms of lymphocytosis.

When to see a doctor

See a doctor urgently if:

• If you have a temperature, night sweats, or unexplained weight loss that lasts more than a few weeks.
• If you notice swollen lymph nodes that are getting bigger or painful.
• If you have easy bruising or unusual bleeding.

Book a routine appointment if:

• If you have had a blood test that showed lymphocytosis and you have no symptoms, wait for your doctor's advice.
• If you are asked to repeat a blood test, make sure you schedule it as recommended.

Diagnosis

Lymphocytosis is diagnosed with a blood test called a complete blood count (CBC) and a 'differential,' which shows the number and type of white blood cells. Your doctor will look at your medical history, symptoms, and any medications you take.

Tests that may be done

• Complete blood count (CBC) with differential.
• Peripheral blood smear – looking at a drop of blood under a microscope.
• Blood tests for specific infections, such as EBV or whooping cough.
• Flow cytometry – a special test that checks the types of lymphocytes, if needed.
• Bone marrow biopsy – rarely needed, but done if a blood cancer is suspected.

What to expect at your appointment

Your doctor will explain what the test results mean and may ask you to repeat the blood test after a few weeks. If there are no symptoms, they may simply watch and wait. If an underlying condition is found, you will be referred to a specialist, such as a hematologist (blood specialist).

Treatment

Lymphocytosis itself is not usually treated – the goal is to treat the cause. If an infection is present, supportive care and rest are often enough. If a serious blood condition is found, treatment will be tailored to that condition.

Self-care at home

• Rest and drink plenty of fluids, especially if you have an infection.
• Practice good handwashing to avoid spreading infections.
• Follow up with your doctor for repeat blood tests as advised.
• Take over-the-counter pain or fever relief only as recommended by a pharmacist or doctor – never take more than the label says.

Medical treatments

For bacterial infections, antibiotics may be prescribed. For autoimmune or inflammatory causes, steroids or anti-inflammatory medicines may be used. If a blood cancer like leukemia is found, treatment may include targeted therapy, chemotherapy, or immunotherapy. Your healthcare team will choose the best plan based on your specific diagnosis and overall health.

When is surgery considered?

Surgery is not used to treat lymphocytosis itself. In rare cases, surgery may be needed to biopsy an enlarged lymph node, but this is just for diagnosis.

Living with this condition

For most people, lymphocytosis is a temporary finding that requires no special daily care. You just need to watch for any new symptoms and keep your doctor appointments. If you have a chronic blood condition, your doctor will give you a follow-up plan.

Lifestyle tips

• Stay up to date with vaccinations to prevent infections.
• Avoid close contact with people who are sick, especially if your immune system is weak.
• Wash your hands often with soap and water.
• Get enough sleep and manage stress.
• Avoid smoking and excessive alcohol.

Diet and exercise

Eat a balanced diet with fruits, vegetables, whole grains, and lean proteins to support your immune system. As long as you feel well, regular gentle exercise like walking can help your energy levels. If you are very tired, rest when you need to.

Mental health and emotional wellbeing

Finding out that a blood test is abnormal can cause worry or anxiety. It is normal to feel concerned. Remember that most cases are harmless, but it is okay to ask your doctor questions. Talking to family or a counselor can also help.

Prevention

Most cases of lymphocytosis cannot be prevented because they are caused by common infections. You can lower your risk by practicing good hygiene, avoiding known infections, and keeping your immune system strong through healthy habits.

Vaccines

Staying up to date with recommended vaccines, such as flu, COVID-19, and other routine immunisations, can reduce the chance of infections that may lead to lymphocytosis.

Screening programmes

Routine screening for lymphocytosis is not recommended for the general public. Blood tests are done when there is a medical reason.

Complications

If left untreated

• If an infection is left untreated, it can become more severe or spread.
• If a chronic blood condition like leukemia is not monitored, it can progress and cause symptoms like severe anemia, frequent infections, or bleeding.
• Rarely, a high lymphocyte count can increase blood thickness, which may affect blood flow – but this is not common.

Long-term outlook

The outlook for lymphocytosis is very good for most people. It usually clears up on its own as the underlying infection resolves. For those with a chronic condition, modern treatments are very effective at controlling the disease, and many people live full, active lives for many years. Your care team will help you understand what to expect.

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