Atypical Lymphocytes

Atypical Lymphocytes

Atypical Lymphocytes also known as reactive lymphocytes or atypical lymphoid cells, are a type of white blood cell that can be observed in the peripheral blood. when a person’s immune system is activated or responding to an infectious or other immune stimulus. These lymphocytes are called Atypical because they appear larger and have an altered appearance compared to normal lymphocytes. They are often characterized by irregular shapes, larger sizes, and a more abundant cytoplasm. Atypical lymphocytes are typically seen on a peripheral blood smear when a healthcare provider suspects an underlying, infection or immune response.

Causes of Atypical Lymphocytes?

  1. Viral Infections:
  • Viral infections are one of the most common causes of atypical lymphocytes.
  • Conditions such as infectious mononucleosis (caused by the Epstein-Barr virus), cytomegalovirus (CMV) infection, and other viral illnesses can trigger an immune response that leads to the production of atypical lymphocytes.

2. Bacterial Infection:

  • Certain bacterial infections, such as pertussis (whooping cough) and tuberculosis, can also elevate atypical lymphocytes.

3. Parasitic Infections:

  • Infectious caused by parasites, like Toxoplasma gondii or Trypanosoma species, can lead to the presence of atypical lymphocytes.

4. Autoimmune Disease:

  • Some autoimmune diseases, like systemic lupus erythematosus (SLE), can cause an increase in atypical lymphocytes as part of the immune system response to self-antigens.

5. Drug Reaction:

  • Certain medications, especially those that can cause drug-induced hypersensitivity reactions, may lead to atypical lymphocytes in the blood.

6. Hematologic Disorders:

  • In rare cases, hematologic disorders such as lymphomas and leukemias may be associated with atypical lymphocytes.


It’s important to note that the presence of atypical lymphocytes in the blood does not provide a definitive diagnosis but indicates an underlying immune response. Additional tests, such as serology, viral studies, or other diagnostic procedures, are atypically needed to determine the specific cause of the atypical lymphocytosis and the appropriate treatment. If you or someone you know has a high count of atypical lymphocytes in the blood, it is crucial to consult a healthcare provider for a thorough evaluation and a diagnosis to address the underlying cause.

What may high levels of atypical lymphocytes indicate?

High levels of atypical lymphocytes in the blood can be indicative of several conditions. Atypical lymphocytes are lymphocytes (a type of white blood cell) that appear unusual in size, shape, or other characteristics when examined under a microscope. These atypical lymphocytes are often associated with an immune system response to infections, such as viral or bacterial infections. Here are some potential causes of high levels of atypical lymphocytes:

  1. Viral Infections: The most common cause of atypical lymphocytosis is viral infections, particularly Epstein-Barr virus (EBV) or mononucleosis. Other viruses like cytomegalovirus (CMV), adenovirus, and hepatitis can also lead to atypical lymphocytes.
  2. Bacterial Infections: Some bacterial infections, like Bordetella pertussis (causing whooping cough) and Mycoplasma pneumoniae (causing walking pneumonia), can result in atypical lymphocytes.
  3. Autoimmune Disorders: Certain autoimmune diseases, like systemic lupus erythematosus (SLE) and rheumatoid arthritis, may lead to atypical lymphocytes.
  4. Drug Reactions: Some medications can cause an abnormal immune response leading to atypical lymphocytosis. For example, phenytoin, which is used for seizures, can lead to this condition.
  5. Lymphoproliferative Disorders: In some cases, high levels of atypical lymphocytes may indicate more serious conditions like lymphoproliferative disorders, including lymphoma and leukemia.
  6. Other Infections: In addition to viral and bacterial infections, other infectious agents, such as parasites, can cause atypical lymphocytosis.

Symptoms and diagnosis of atypical lymphocytes:

Here are some common symptoms and methods of diagnosis related to atypical lymphocytes:


  1. Fatigue: Generalized fatigue and weakness may occur due to an underlying illness that leads to the production of atypical lymphocytes.
  2. Sore Throat: If atypical lymphocytes are caused by a viral infection, a sore throat is a common symptom.
  3. Swollen Lymph Nodes: Enlarged lymph nodes, especially in the neck, underarms, or groin, can be a sign of atypical lymphocyte activity in response to an infection.
  4. Fever: An elevated body temperature often accompanies infections associated with atypical lymphocytes.
  5. General Malaise: A feeling of overall discomfort or unwellness may be experienced.


  1. Blood Tests: A complete blood count (CBC) may reveal an increased number of atypical lymphocytes in the blood. This can prompt further investigation.
  2. Peripheral Blood Smear: A peripheral blood smear involves looking at a drop of blood under a microscope to identify and examine the morphology of blood cells, including atypical lymphocytes. These cells are larger than normal lymphocytes and have irregular shapes and nuclei.
  3. Medical History and Physical Examination: Your doctor will inquire about your medical history and perform a physical examination to assess your symptoms, including checking for swollen lymph nodes and signs of infection.
  4. Viral Testing: If a viral infection is suspected, specific tests may be conducted to identify the causative virus. For example, the Epstein-Barr virus (EBV) is a common cause of atypical lymphocytes and can be confirmed through serological tests.
  5. Additional Blood Tests: Depending on the clinical context and suspected underlying causes, your doctor may order additional blood tests, such as serology tests for autoimmune diseases or specific markers for malignancies like lymphoma.
  6. Imaging: In some cases, imaging studies such as ultrasound, CT scans, or MRI may be used to examine lymph nodes and other organs to identify potential underlying conditions.

By Mehfooz Ali

Explore the fascinating journey of Mehfooz Ali, a renowned website developer diving into the world of blogging. Discover insights, tips, and inspirations for your blogging endeavors. Click now for an enriching experience.

Leave a Reply

Your email address will not be published. Required fields are marked *