What Is iMCD

Understanding iMCD and Why It Can Be a Long Road to Diagnosis

If you or a loved one has been diagnosed with idiopathic multicentric Castleman disease (iMCD), you probably have a lot of questions. Let’s start by helping you understand what iMCD is and how it differs from the infectious, autoimmune, cancerous, or other lymphoproliferative disorders it mimics. 

iMCD can be very difficult to diagnose because it imitates the disorders mentioned above. The doctors will have to rule out all of these conditions before they can confirm iMCD, which can take a few days to several weeks.


Castleman Disease and Its Subtypes

Castleman disease (CD) is a rare condition that affects the lymph nodes.

Lymph nodes normally create immune cells that help to fight infections. In CD, there is an abnormal overgrowth of these cells, which causes the lymph nodes to appear swollen, resembling a tumor. However, these growths are not cancerous.

There are 2 main types of CD: 

Unicentric Castleman disease (UCD)

UCD involves a single group of lymph nodes anywhere in the body that can be treated with surgical removal.

Multicentric Castleman disease (MCD)

MCD affects multiple groups of lymph nodes throughout the body. This condition is further categorized into 2 different types:

  • Human herpesvirus‑8 (HHV-8)–positive MCD, which can cause Kaposi’s sarcoma—a rare cancer in which lesions grow on the skin, mouth, nose, throat, and other parts of the body
  • Human immunodeficiency virus (HIV)–negative and HHV-8–negative MCD, also known as idiopathic multicentric Castleman disease (iMCD)
Idiopathic multicentric Castleman disease (iMCD)

iMCD is rare and can occur at any age, resulting from a cytokine storm that is often driven by interleukin‑6 (IL‑6).

Unicentric Castleman disease Multicentric Castleman disease
Idiopathic multicentric Castleman disease (iMCD)

is rare and can occur at any age, resulting from a cytokine storm that is often driven by interleukin-6 (IL-6).

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Did you know?

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There are approximately 30,000 Americans afflicted with one of the types of Castleman disease, which is roughly the same number as amyotrophic lateral sclerosis (ALS) and cystic fibrosis. Every year, approximately 1650 patients in the United States are diagnosed with new cases of MCD.

A 3D rendering of IL-6, a protein found in overabundance in people with idiopathic multicentric Castleman disease.

Understanding iMCD and the Importance of Cytokines

Idiopathic multicentric Castleman disease (iMCD) is a rare disorder in which the body overproduces various cytokines. Cytokines are powerful molecules that are normally secreted by the cells of the immune system in response to infectious or noninfectious agents.

If these overabundant cytokines are quickly released into the bloodstream, a cytokine storm can occur, with potentially severe or life-threatening effects. In the case of people with iMCD, the cytokine interleukin-6, or IL-6, may be responsible for the storm.


Symptoms of iMCD

Common Clinical Symptoms of iMCD

 iMCD can be very difficult to diagnose because its presentation can vary, causing it to be mistaken for other conditions. If iMCD is not diagnosed and treated with the proper medication, it could lead to organ failure and other life-threatening conditions. 

The following are symptoms commonly observed in patients with iMCD:

Fluid accumulation:Swelling caused by excess fluid trapped in body tissues. Lymph node swelling:Enlarged or swollen lymph nodes may be found throughout the body. In some cases, they may be detected by gently pressing on the area of the body in question. Enlarged organs:The liver or spleen may be larger than normal. Your doctor may test for an enlarged liver or spleen by examining your abdomen. Blood tests, ultrasound, or magnetic resonance imaging (MRI) may support the diagnosis. Flu-like symptoms:Fevers, night sweats, fatigue, and weight loss.

If you are a patient or a caregiver, be sure to report even common flu-like symptoms to your doctor. 

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Image of a nurse and a patient in a hospital. Idiopathic multicentric Castleman disease patients may require an excisional biopsy to confirm the disease.


An Excisional Biopsy Is the Most Effective Way to Confirm iMCD

A diagnosis of iMCD requires the examination of an affected lymph node. Your doctor may perform a needle biopsy (core biopsy) first to look for more common causes of your symptoms, but this is generally not sufficient to confirm iMCD. 

During an excisional biopsy, a doctor will remove the affected lymph node. It is an invasive procedure that is performed under general anesthesia and may require hospitalization. Talk to your doctor if you have any questions about this procedure. 

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