Thymic Hyperplasia: Causes, Symptoms and Treatment

Medically Reviewed on 5/17/2023

What is thymic hyperplasia?

Thymic hyperplasia refers to the enlargement or overgrowth of the thymus gland—a part of the immune system located in the chest between the lungs and behind the breastbone. It is a noncancerous condition characterized by an increase in the number and size of the cells in the thymus.

Thymic hyperplasia can occur due to various reasons, including normal physiological changes during childhood and adolescence, certain medical conditions, or a response to an increased demand for immune cells. It is commonly seen in infants and children as the thymus plays a crucial role in the development and maturation of immune cells during early life.

Thymic hyperplasia is usually asymptomatic and discovered incidentally during imaging tests, such as chest X-rays or CT scans. In some cases, it may cause symptoms such as chest pain, cough, or difficulty breathing if the enlarged thymus compresses nearby structures.

The treatment of thymic hyperplasia depends on the underlying cause and presence of symptoms. In most cases, no treatment is required, and the condition resolves on its own over time. However, if symptoms are present or the hyperplasia is associated with an underlying medical condition, further evaluation, and management may be necessary. This can include medication, surgery to remove the thymus gland (thymectomy), or other targeted therapies as determined by the doctor based on the individual's specific situation.

What is the function of the thymus gland?

The thymus gland is a specialized organ of the immune system located in the upper chest behind the sternum (breastbone). It plays a crucial role in the development and maturation of T-lymphocytes—a type of white blood cell that is vital for immune responses.

Important functions of the thymus gland may include:

  • T-cell maturation: The thymus is primarily responsible for the maturation of T-cells produced in the bone marrow. Immature T-cells migrate to the thymus, where they undergo thymic education through positive and negative selection. During this process, T-cells that recognize and bind to the body's proteins (self-antigens) too strongly are eliminated to prevent autoimmune reactions.
  • Hormone production: The thymus gland produces several essential hormones for T-cell development and function. The most important hormone is thymosin, which helps in the differentiation and maturation of T-cells. Thymopoietin, thymulin, and interleukins are other hormones produced by the thymus that contribute to T-cell development and the regulation of the immune system.
  • Immune system regulation: The thymus gland plays a crucial role in immune system regulation. It helps orchestrate the overall balance and coordination of immune responses by producing specialized T-cells with specific functions, such as helper T-cells, cytotoxic T-cells, and regulatory T-cells. These T-cells recognize and eliminate infected cells, cancer cells, and foreign substances in the body.
  • Neonatal immunity: The thymus is particularly active during early life, especially in the prenatal and neonatal periods. It aids in the development of a functional immune system in infants, ensuring the production of a diverse repertoire of T-cells capable of recognizing a wide range of pathogens. The thymus starts to decline in size and function after puberty, gradually replaced by fatty tissue.

The thymus gland plays a critical role in the development, maturation, and regulation of T-cells, which are vital for effective immune responses. By producing hormones and facilitating T-cell selection, the thymus helps shape the immune system's ability to recognize and respond to foreign invaders while minimizing the risk of autoimmune reactions.

What are the different types of thymic hyperplasia?

There are several types of thymic hyperplasia, each with unique characteristics. The eight main types include:

  1. Physiological (normal) thymic hyperplasia: A common type of thymic hyperplasia that occurs as a normal response to the body's increased demand for immune function. It can be seen in infants, children, and adolescents during periods of growth and development.
  2. Reactive (inflammatory) thymic hyperplasia: Occurs in response to various inflammatory conditions such as infections, autoimmune disorders, and allergic reactions. It is characterized by an increase in the number of immune cells within the thymus.
  3. Lymphoid thymic hyperplasia: Involves an overgrowth of lymphoid tissue within the thymus. It is commonly associated with myasthenia gravis (MG)—an autoimmune neuromuscular disorder.
  4. Germinal center hyperplasia: Germinal centers are regions within lymphoid tissues where B cells proliferate and differentiate. Thymic hyperplasia with germinal centers is often associated with autoimmune diseases, such as rheumatoid arthritis, or certain infections.
  5. Focal thymic hyperplasia: Focal thymic hyperplasia is the localized enlargement of a specific area or nodule within the thymus. It can sometimes be mistaken for a thymic tumor or mass.
  6. Cortical thymic hyperplasia: Primarily affects the outer cortical region of the thymus. It is often associated with autoimmune disorders such as systemic lupus erythematosus.
  7. Medullary thymic hyperplasia: Involves excessive growth of the inner medullary region of the thymus. It can be seen in various conditions, including MG, Graves' disease, and other autoimmune disorders.
  8. True thymic hyperplasia: Refers to a genuine increase in the size and cellularity of the thymus. It can occur in response to various factors, including genetic mutations, endocrine abnormalities, and immunodeficiency states.

Thymic hyperplasia is a reactive process that responds to certain stimuli, such as infections or autoimmune disorders. Thymic hyperplasia can sometimes mimic more serious conditions such as thymoma, a tumor of the thymus gland, so a thorough evaluation by a healthcare professional is necessary for accurate diagnosis and appropriate management.

What is the most common cause of thymic hyperplasia?

Thymic hyperplasia can have various causes, including:

  • Physiological thymic hyperplasia: This normal and temporary enlargement of the thymus occurs during childhood. It is a part of the natural development and maturation of the immune system.
  • Reactive thymic hyperplasia: It occurs as a response to certain medical conditions or stimuli. Some causes include:
    • Infections: Certain infections, such as viral infections (respiratory syncytial virus and Epstein-Barr virus) or bacterial infections (Mycobacterium tuberculosis), can trigger thymic hyperplasia as the immune system responds to fight off the infection.
    • Autoimmune diseases: Conditions such as myasthenia gravis, systemic lupus erythematosus, and rheumatoid arthritis may cause an immune response that leads to thymic hyperplasia.
    • Allergic reactions: Severe allergic reactions or hypersensitivity responses can stimulate thymic hyperplasia as the immune system mounts a response.
    • Steroid therapy: Long-term use of corticosteroids or other immunosuppressive medications may lead to reactive thymic hyperplasia as the thymus tries to compensate for the suppression of the immune system.
    • Chemotherapy: Certain chemotherapeutic agents used in cancer treatment can cause thymic hyperplasia as a side effect.
    • Radiation therapy: Radiation treatment in the chest area, commonly used in the treatment of lymphomas or breast cancer, may induce thymic hyperplasia.
    • Lymphoproliferative disorders: Conditions characterized by abnormal growth of lymphoid cells, such as Hodgkin's lymphoma, non-Hodgkin lymphoma, or leukemia, can cause thymic hyperplasia.
    • Immunodeficiency disorders: Some primary immunodeficiency disorders, such as DiGeorge syndrome or severe combined immunodeficiency, can present with thymic hyperplasia due to impaired immune system development.
    • Hormonal imbalance: Rarely, hormonal disturbances, such as excessive production of growth hormone or cortisol, can contribute to thymic hyperplasia.

Thorough evaluation by a healthcare professional, including medical history, physical examination, and diagnostic tests, is necessary to determine the underlying cause of thymic hyperplasia in an individual case.


Where is the thyroid gland located? See Answer

What are the symptoms of thymic hyperplasia?

Thymic hyperplasia may not always cause noticeable symptoms, and it can be associated with certain conditions or present with specific manifestations.

Here are some of the symptoms and details related to thymic hyperplasia:

  • Chest discomfort: Thymic hyperplasia can cause a sensation of pressure, fullness, or discomfort in the chest due to the enlarged thymus pressing against nearby structures.
  • Difficulty breathing: When the thymus gland grows larger, it can potentially compress the airways, leading to breathing difficulties. This may manifest as shortness of breath, wheezing, or a sense of breathlessness.
  • Cough: Thymic hyperplasia can sometimes irritate the airways, resulting in a persistent cough. This cough may be dry or accompanied by the production of mucus.
  • Superior vena cava syndrome (SVCS): In rare cases, an enlarged thymus gland can compress the superior vena cava—a large vein that carries blood from the upper body to the heart. This compression can lead to SVCS, characterized by symptoms such as swelling of the face, neck, or arms; difficulty swallowing; and prominent veins on the chest.
  • Myasthenia gravis (MG): Thymic hyperplasia is commonly associated with MG, an autoimmune disorder affecting muscles. In MG, the immune system mistakenly targets the neuromuscular junctions, leading to muscle weakness and fatigue. Symptoms of MG may include drooping eyelids, double vision, difficulty speaking and swallowing, and muscle weakness in the limbs.

Thymic hyperplasia itself may not always cause symptoms and is often discovered incidentally during medical imaging or surgical procedures performed for unrelated reasons. If a patient suspects they have thymic hyperplasia or experiences concerning symptoms, they must consult a healthcare professional for an accurate diagnosis and appropriate management.

Is thymic hyperplasia painful?

Thymic hyperplasia is typically not associated with pain. In most cases, it is asymptomatic and discovered incidentally during imaging studies. However, if thymic hyperplasia causes compression of nearby structures, such as the airways or blood vessels, it may lead to symptoms such as shortness of breath, coughing, or chest discomfort.

If a patient experiences any concerning symptoms, they must consult a healthcare professional for a proper evaluation and diagnosis.

How long does thymic hyperplasia last?

The duration of thymic hyperplasia can vary depending on the underlying cause and individual factors. In general, thymic hyperplasia can be classified as either transient or persistent.

  • Transient thymic hyperplasia is a temporary enlargement of the thymus gland and typically resolves on its own within a few months to a year. It is commonly seen in infants and children and is often associated with normal immune system development.
  • Persistent thymic hyperplasia refers to a prolonged or chronic enlargement of the thymus gland. It can be caused by various factors such as autoimmune diseases, certain infections, and some types of tumors. The duration of persistent thymic hyperplasia depends on the underlying cause and how it is managed. Treatment may involve addressing the underlying condition, and the size of the thymus gland may gradually decrease with appropriate management.

Thymic hyperplasia should be evaluated and managed by a healthcare professional. They can provide a more accurate prognosis based on the individual's circumstances and medical history.

When should you see a doctor for thymic hyperplasia?

Thymic hyperplasia is typically a benign condition. Patients must seek medical attention if they suspect thymic hyperplasia.

Here are some indicators of when to see a doctor:

  • Persistent symptoms: If a patient experiences persistent symptoms such as chest pain, difficulty breathing, coughing, or wheezing, they must consult a doctor. These symptoms may indicate thymic hyperplasia or other underlying conditions that require medical evaluation.
  • Rapid or significant enlargement of the neck: If a patient notices a rapid or significant enlargement of their neck, particularly in the area above their breastbone, it could be related to thymic hyperplasia. A prompt medical assessment is recommended to determine the cause and ensure appropriate management.
  • Concerning imaging findings: Thymic hyperplasia is often detected incidentally on imaging studies, such as chest X-rays or CT scans. If a healthcare professional notices an abnormality suggestive of thymic hyperplasia, further evaluation will be necessary to confirm the diagnosis and assess its implications.
  • Unexplained symptoms in children: Thymic hyperplasia is more commonly observed in children. If a child exhibits unexplained symptoms such as recurrent respiratory infections, poor weight gain, or developmental delays, it is crucial to have them evaluated by a pediatrician.
  • Medical history and risk factors: If a patient has a medical history of autoimmune disorders, immunodeficiency, or cancer, they may be at an increased risk of thymic hyperplasia. In such cases, it is prudent to consult a healthcare provider to assess the need for evaluation and monitoring.

If a patient suspects thymic hyperplasia or has concerns about their health, they must schedule an appointment with a doctor for a thorough evaluation.

What kind of doctor treats thymic hyperplasia?

The treatment of thymic hyperplasia typically involves a multidisciplinary approach, and various healthcare professionals may be involved in the care of a patient with this condition. 

Here are the doctors who may be involved in the treatment of thymic hyperplasia:

  • Primary care physician (PCP): The first point of contact for most patients is their PCP. They are responsible for initial evaluation, diagnosis, and coordination of further care.
  • Pulmonologist: As the thymus gland is located in the chest, a pulmonologist (lung specialist) may be involved in the evaluation and treatment of thymic hyperplasia, particularly if it is causing respiratory symptoms or affecting lung function.
  • Endocrinologist: The thymus gland is a part of the endocrine system, and an endocrinologist specializes in diagnosing and managing conditions related to hormonal imbalances. They may be consulted if the thymic hyperplasia is associated with hormonal abnormalities.
  • Thoracic surgeon: In some cases, surgical intervention may be necessary to remove the enlarged thymus gland. A thoracic surgeon is a specialist who performs surgeries involving the chest and may be involved in treating thymic hyperplasia.
  • Radiologist: A radiologist may order imaging studies such as chest X-rays, CT scans, or MRI scans to evaluate the size and characteristics of the thymus gland. They interpret these images and provide valuable information on diagnosis and treatment planning.
  • Immunologist: The thymus gland is crucial for the development and maturation of immune cells. An immunologist specializes in disorders of the immune system and may be involved in the management of thymic hyperplasia, particularly if it is associated with immune-related conditions or complications.
  • Oncologist: Thymic hyperplasia can sometimes mimic or coexist with thymic tumors, which can be cancerous. In such cases, an oncologist (who specializes in treating cancer) may be involved in the evaluation and management.

The exact combination of doctors involved in the treatment of thymic hyperplasia may vary depending on the specific circumstances and symptoms of each patient. Collaboration among these specialists ensures comprehensive care tailored to the individual needs of the patient.

How do doctors diagnose thymic hyperplasia?

Diagnosing thymic hyperplasia involves a series of steps to evaluate the thymus gland and rule out other potential causes of thymic enlargement.

Here is a step-by-step explanation of the diagnostic process:

  • Medical history
    • The doctor will start by taking a detailed medical history, including any symptoms experienced by the patient, such as chest pain, shortness of breath, or difficulty swallowing. Moreover, they will inquire about any underlying medical conditions or recent infections that might contribute to thymic hyperplasia.
  • Physical examination
    • The doctor will conduct a thorough physical examination to assess for signs of thymic hyperplasia, such as a visible bulge or enlargement in the neck or upper chest area. They will also listen to the patient's lungs and heart to check for abnormal sounds.
  • Imaging studies
    • Chest X-ray: It is commonly the initial imaging test performed and provides a basic assessment of the thymus gland's size, shape, and position within the chest cavity. Thymic hyperplasia typically presents as an enlarged thymus on X-ray.
    • CT scan: If the chest X-ray shows an enlarged thymus or if further evaluation is necessary, the doctor may order a CT scan. CT imaging provides more detailed cross-sectional images of the thymus gland and surrounding structures, allowing for a better assessment of the size, shape, and characteristics of the thymus. It can help differentiate thymic hyperplasia from other thymic abnormalities or tumors.
  • Blood tests
    • The doctor may order blood tests to assess specific markers associated with thymic hyperplasia or to rule out other potential causes. These tests may include a complete blood count, an autoimmune panel, or specific tumor markers.
  • Biopsy
    • In certain cases, a biopsy may be necessary to confirm the diagnosis of thymic hyperplasia or to rule out other potential causes. This is typically done through a minimally invasive procedure called a mediastinoscopy, in which a small tissue sample is obtained from the thymus gland for microscopic examination.
  • Other tests
    • Depending on the clinical presentation and findings from previous tests, additional evaluations such as MRI, PET scan or genetic testing may be considered in some cases to further characterize the thymus or identify underlying causes.

The diagnostic process may vary depending on individual circumstances, and the specific tests ordered may differ from case to case. A qualified healthcare professional will determine the most appropriate diagnostic approach based on the patient's clinical presentation and suspected underlying cause.

How do you treat thymic hyperplasia?

Thymic hyperplasia refers to the enlargement or overgrowth of the thymus gland. It can be caused by various factors, including normal physiological changes, autoimmune diseases, infections, or certain medications. The treatment of thymic hyperplasia depends on the underlying cause and severity of symptoms.

Here are the different ways thymic hyperplasia can be treated:

  • Observation and monitoring
    • In mild cases of thymic hyperplasia without significant symptoms, a "wait and watch" approach may be adopted. Regular monitoring with imaging tests, such as chest X-rays or CT scans, can be done to track the size of the thymus and ensure there is no progression or development of complications.
  • Medications
    • If thymic hyperplasia is associated with an underlying autoimmune condition, such as myasthenia gravis, treatment may involve medications to manage the autoimmune disease. This can include immunosuppressants, such as corticosteroids or other immune-modulating drugs, which can help reduce inflammation and control symptoms.
  • Surgical intervention
    • Surgery may be considered in cases of severe or symptomatic thymic hyperplasia. The most common surgical procedure is thymectomy, which involves the removal of the thymus gland. Thymectomy can be done through open surgery or minimally invasive techniques, such as video-assisted thoracoscopic surgery or robotic-assisted surgery. It is typically performed by a thoracic surgeon and can help alleviate symptoms and prevent complications.
  • Radiation therapy
    • In some cases, radiation therapy may be used as a treatment option, particularly when thymic hyperplasia is associated with malignancy or if surgery is not feasible. Radiation therapy involves using high beams of energy X-rays or other forms of radiation to target and destroy abnormal thymic tissue.
  • Treatment of underlying conditions
    • If thymic hyperplasia is caused by an underlying infection or medication, addressing and treating the primary cause can lead to regression of thymic hyperplasia. This may involve the use of antibiotics to clear an infection or the discontinuation of medications known to cause thymic hyperplasia.

Consult a healthcare professional for an accurate diagnosis and to determine the most appropriate treatment approach for thymic hyperplasia based on the circumstances.

Subscribe to MedicineNet's General Health Newsletter

By clicking Submit, I agree to the MedicineNet's Terms & Conditions & Privacy Policy and understand that I may opt out of MedicineNet's subscriptions at any time.

Medically Reviewed on 5/17/2023
Thymic Hyperplasia:

Imaging Characteristics of Pathologically Proven Thymic Hyperplasia: Identifying Features That Can Differentiate True from Lymphoid Hyperplasia:

Thymic hyperplasia with massive enlargement:

Imaging of thymic disorders: