Castleman Disease

Castleman disease refers to a group of rare disorders that involve a hyperactive immune system. In people who are healthy, their immune system activates to fight off invaders like bacteria or viruses but then settles back down, watching and waiting for the next time it’s needed. In people with Castleman disease, their immune system continues to remain activated and leads to a chronic hyper-inflammatory state that can damage multiple organs and even cause death.

Lymph nodes (tiny organs) work with your immune system to filter substances from your body. When you’re sick, your lymph nodes work harder to clear the bacteria or virus, along with the cells your body makes to fight them. This causes an overgrowth of cells in your lymph nodes, making these nodes bigger (swell).

In Castleman disease, one or more of your lymph nodes become enlarged. And they don’t just get bigger. When your doctor looks at a sample of your lymph node (a biopsy) under a microscope or analyzes them using different staining, they can see changes in the tissue.

What are the different types of Castleman disease?

Castleman disease is currently classified as unicentric or multicentric based on how many regions of your body have enlarged lymph nodes. The differences between unicentric and multicentric Castleman disease are important because each type requires different treatments.

Unicentric Castleman disease (UCD)

Unicentric Castleman disease (UCD) — or localized Castleman disease — causes enlargement of one or more lymph nodes in one area (region) of your body. The causes of UCD are unknown.

Multicentric Castleman disease (MCD)

Multicentric Castleman disease (MCD) causes lymph node enlargement in multiple regions of your body. There are three categories of MCD: POEMS-associated MCD, HHV-8-associated MCD and idiopathic MCD.

• POEMS-associated MCD: POEMS is a rare blood disorder that sometimes accompanies MCD. POEMS gets its name from its associated signs and symptoms. They include polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder and skin changes.
• HHV-8-associated MCD: Human herpes virus-8 (HHV-8) is a common virus. Most people who have it don’t get sick. You’re more likely to have HHV-8-associated MCD if you’re HIV positive or if you have another condition that makes you more susceptible to infections (immunocompromised).
• Idiopathic MCD (iMCD): The most common form of MCD is idiopathic. “Idiopathic” means that its causes are unknown.

There are three types of iMCD:

• iMCD associated with TAFRO: TAFRO syndrome sometimes accompanies iMCD. TAFRO gets its name from its associated signs and symptoms, including thrombocytopenia (low platelets), anasarca (swelling from fluid build-up), fever, renal (kidney) dysfunction and organomegaly (enlarged spleen or liver).
• iMCD with idiopathic plasmacytic lymphadenopathy (iMCD-IPL): People with IMCD-IPL may have too many platelets in their blood (thrombocytosis), and their white blood cells may make too many proteins called antibodies.
• iMCD, not otherwise specified (iMCD-NOS): iMCD-NOS has unknown causes and isn’t associated with TAFRO or POEMS.