Castleman disease is a rare disorder that causes lymph nodes to grow abnormally large. It happens when the immune system stays switched on, even when there is no infection to fight. This constant activity leads to long-term inflammation that can damage organs throughout the body. In serious cases, it can be life-threatening. This article explains what Castleman disease is, who it affects, and what treatment options are available to Canadians.
What Is Castleman Disease?
In a healthy person, the immune system activates when it detects a threat — like bacteria or a virus. Once the threat is gone, the immune system calms back down. However, people with Castleman disease have an immune system that stays highly active, even without a real threat present.
This ongoing immune activity causes chronic inflammation throughout the body. As a result, the lymph nodes — small glands that are a key part of the immune system — swell up and grow much larger than normal. Over time, this inflammation can lead to organ failure.
Castleman disease is not officially classified as a cancer, an autoimmune disease, or an infectious disease. Researchers are still working to fully understand it. Some other conditions, including certain cancers and autoimmune diseases, can cause similar changes in the lymph nodes, which makes diagnosis more complex.
Types of Castleman Disease
There are two main types of Castleman disease. They differ based on how many areas of the body are affected.
Unicentric Castleman Disease (UCD)
Unicentric Castleman disease affects only one group of lymph nodes in one region of the body. This is the less severe form. Many people with UCD have no symptoms at all — a swollen lymph node may be the only sign.
UCD is more commonly diagnosed in people between the ages of 30 and 40. It affects men and women equally. The exact cause of UCD is currently unknown.
Multicentric Castleman Disease (MCD)
Multicentric Castleman disease affects lymph nodes in multiple regions of the body at once. This form is more serious and harder to treat. MCD is more common in people over 50 and is somewhat more frequent in men.
MCD is further divided into three subtypes:
HHV-8-associated MCD: Human herpesvirus 8 (HHV-8) is a common virus. Most people carry it without getting sick. However, people with weakened immune systems — such as those living with HIV — can develop Castleman disease as a result of HHV-8 infection.
POEMS-associated MCD: POEMS is a rare blood disorder that is sometimes linked to multicentric Castleman disease. It affects multiple body systems at once.
Idiopathic MCD (iMCD): This is the most common subtype of MCD. “Idiopathic” means the cause is unknown. Researchers are actively studying why this form develops.
How Common Is Castleman Disease?
Castleman disease is rare. Each year, between 4,300 and 5,200 people are diagnosed with it — most of these figures come from American data, but the condition affects people worldwide, including Canadians. It can develop in anyone, at any age.
Unicentric Castleman disease is most often diagnosed in adults in their 30s and 40s. The multicentric form tends to appear in people over 50. Because the disease is rare, it is often misdiagnosed or diagnosed late.
Causes and Risk Factors
The exact cause of Castleman disease is not fully understood. However, researchers have identified several factors that may increase the risk of developing it.
HHV-8 infection: Infection with human herpesvirus 8 is linked to some cases, particularly in people with weakened immune systems.
HIV infection: People living with HIV have a higher risk of developing Castleman disease, especially the HHV-8-associated form.
Weakened immune system: Any condition or medication that lowers immunity may increase risk.
Genetic mutations: Certain genetic changes may play a role in some cases.
Autoimmune mechanisms: The immune system may mistakenly attack the body’s own tissues, contributing to the disease.
For more information on how the immune system works, visit Health Canada’s official health resources.
Signs and Symptoms of Castleman Disease
Symptoms of Castleman disease depend on the type. The unicentric form often causes no noticeable symptoms. In many cases, a swollen lymph node is found accidentally during a medical exam for another reason.
The multicentric form tends to produce more obvious and wide-ranging symptoms. These may include:
Fever
Night sweats
Unexplained weight loss
Fatigue and weakness
Nausea and vomiting
Abnormally swollen lymph nodes
An enlarged spleen (splenomegaly)
An enlarged liver (hepatomegaly)
Tingling or numbness in the hands and feet
Swelling in the legs
Abdominal bloating
Anaemia (low red blood cell count)
These symptoms can look very similar to those of other conditions, including the flu, lymphoma, or autoimmune diseases. This is why proper testing is essential for an accurate diagnosis. You can learn more about lymph node conditions at the Mayo Clinic’s patient education centre.
How Is Castleman Disease Diagnosed?
Because Castleman disease shares symptoms with many other illnesses, your doctor will need to rule out other conditions first. The diagnostic process typically involves several steps.
Lymph Node Biopsy
A biopsy is the only way to confirm a diagnosis of Castleman disease. Your doctor will remove a small piece of tissue — or sometimes the entire lymph node — and send it to a laboratory. Pathologists examine the tissue under a microscope and look for specific changes that indicate an overactive immune response. The biopsy result can also reveal which type of Castleman disease is present.
Blood and Urine Tests
Your doctor will order blood tests to check for signs of anaemia, abnormal platelet counts, and inflammation markers. A urine sample may also be collected. Blood tests will typically include an HIV test, since HIV infection is a known risk factor for Castleman disease.
Imaging Tests
Tests such as X-rays, MRI scans, and PET-CT scans help doctors locate swollen lymph nodes throughout the body. Imaging can also reveal whether the liver or spleen are enlarged. These results help doctors determine which type of Castleman disease is present and how widespread it is.
Treatment Options for Castleman Disease
Treatment for Castleman disease depends on the type and how severe it is. Your care team will develop a plan based on your specific situation.
Treating Unicentric Castleman Disease
Surgery is the first-choice treatment for unicentric Castleman disease. The goal is to remove the affected lymph node entirely. In many cases, surgical removal leads to a full recovery.
If the lymph node is in a difficult location, or if it is very large, your doctor may recommend radiation therapy or immunotherapy before surgery. These treatments can shrink the node and make surgery safer and easier. If you have no symptoms and the node is small, your doctor may suggest a “watch and wait” approach — monitoring the condition closely without immediate treatment.
Treating Multicentric Castleman Disease
Multicentric Castleman disease is much harder to treat because it affects many areas of the body at once. Surgery alone is not an effective option. Instead, doctors use a combination of medications, which may include:
Corticosteroids: These reduce inflammation and help relieve symptoms quickly.
Chemotherapy: These drugs slow down the growth of cells in the lymph nodes.
Immunotherapy (monoclonal antibodies): These are lab-made proteins that help regulate the immune system. Siltuximab, for example, is a monoclonal antibody approved specifically for idiopathic MCD. It works by blocking a protein called interleukin-6 (IL-6), which drives the overactive immune response.
Antiviral medications: For HHV-8-associated MCD, antiviral drugs may be part of the treatment plan.
Treatment for MCD is ongoing and may need to be adjusted over time. Regular follow-up with your specialist is essential. For a broader overview of rare disease treatment in Canada, Healthline’s rare disease resource centre offers helpful background information.
When to See a Doctor
You should speak with your family doctor if you notice a lump or swelling in your neck, armpits, or groin that does not go away within a few weeks. This is especially important if the swelling is painless or growing larger over time.
If you also have symptoms like unexplained weight loss, night sweats, or persistent fatigue, do not wait. Book an appointment with your family doctor as soon as possible. If your regular doctor is not immediately available, a walk-in clinic can be a good first step. Many provincial health plans cover these visits at no direct cost to you.
Early diagnosis gives you more treatment options and a better chance of a good outcome. Always consult a qualified healthcare provider before drawing any conclusions about your health based on symptoms alone.
Frequently Asked Questions About Castleman Disease
Is Castleman disease a type of cancer?
Castleman disease is not officially classified as a cancer, although it shares some features with lymphoma. It is a rare immune disorder that causes lymph nodes to grow abnormally large. Researchers are still studying its exact nature, and it currently sits in its own category separate from cancer, autoimmune disease, and infectious disease.
Can Castleman disease be cured?
Unicentric Castleman disease can often be cured through surgical removal of the affected lymph node. Multicentric Castleman disease is more difficult to treat and may require long-term medication management. Many patients with multicentric Castleman disease are able to achieve remission with the right treatment plan.
What causes Castleman disease?
The exact cause of Castleman disease is not fully known. In some cases, it is linked to infection with human herpesvirus 8 (HHV-8), particularly in people with weakened immune systems. In other cases, the cause is entirely unknown, and this is referred to as idiopathic Castleman disease.
How rare is Castleman disease in Canada?
Castleman disease is very rare, with an estimated 4,300 to 5,200 new cases diagnosed each year in North America. Because Canada’s population is about one-tenth the size of the United States, Canadian cases are relatively few each year. Its rarity means it is sometimes missed or misdiagnosed by healthcare providers who are unfamiliar with it.
What are the early signs of Castleman disease?
The early signs of Castleman disease can vary depending on the type. The unicentric form may cause nothing more than a painless swollen lymph node. The multicentric form may cause fever, night sweats, fatigue, and unexplained weight loss — symptoms that are easy to confuse with other illnesses like the flu or lymphoma.
Which doctors treat Castleman disease in Canada?
Castleman disease is typically managed by a team of specialists, including haematologists (blood disorder specialists) and oncologists. Your family doctor or a walk-in clinic physician can refer you to the appropriate specialist through your provincial health plan. Because the disease is rare, some patients are referred to academic health centres with experience in rare immune disorders.
Key Takeaways
Castleman disease is a rare disorder where the immune system stays overactive, causing lymph nodes to swell and leading to chronic inflammation.
There are two main types: unicentric (one area affected) and multicentric (many areas affected). Multicentric is the more serious form.
Common symptoms of the multicentric form include fever, night sweats, fatigue, unexplained weight loss, and swollen lymph nodes.
Diagnosis requires a lymph node biopsy, along with blood tests and imaging scans.
Unicentric Castleman disease is often cured with surgery. Multicentric disease requires ongoing medication, including immunotherapy and corticosteroids.
If you notice a persistent swollen lymph node or related symptoms, speak with your family doctor or visit a walk-in clinic covered by your provincial health plan.
Always consult a qualified healthcare provider for a proper diagnosis and personalised treatment plan.
