Castleman Disease

• Castleman Disease is a rare disorder characterized by the overgrowth of immune cells in lymph nodes and sometimes other organs.
• It presents in two main forms: unicentric, affecting a single lymph node or region, and multicentric, impacting multiple lymph node regions and organs.
• Symptoms vary widely depending on the type, ranging from asymptomatic masses to severe systemic inflammation.
• Diagnosis typically involves a lymph node biopsy, alongside imaging and blood tests.
• Treatment approaches differ by type, with surgery often curative for unicentric disease and systemic therapies for multicentric forms.

What is Castleman Disease? Causes and Types

Castleman Disease is a rare lymphoproliferative disorder characterized by the non-cancerous overgrowth of immune cells in lymph nodes. It can manifest in various ways, from a single enlarged lymph node to a widespread condition affecting multiple lymph nodes and organs throughout the body. Understanding the causes and types of Castleman disease is crucial for accurate diagnosis and effective management.

The exact cause of Castleman Disease is often unknown, but it is believed to involve dysregulation of the immune system. In some cases, particularly with multicentric Castleman Disease, it is associated with human herpesvirus 8 (HHV-8) infection or other underlying conditions like HIV. The disease is broadly categorized into two main types:

• Unicentric Castleman Disease (UCD): This is the more common and generally less severe form, where the disease affects a single lymph node or a group of lymph nodes in one anatomical region. Patients with UCD often experience localized symptoms or may be asymptomatic, with the enlarged lymph node discovered incidentally.
• Multicentric Castleman Disease (MCD): This form is more aggressive and involves multiple lymph node regions and often other organs, such as the spleen, liver, and bone marrow. MCD is associated with systemic symptoms like fever, fatigue, night sweats, and weight loss, and can lead to severe organ dysfunction if left untreated.

While UCD is typically localized and less complex, MCD can be further classified based on its association with HHV-8 (HHV-8-associated MCD) or its idiopathic nature (idiopathic MCD, or iMCD), where no clear cause is identified.

Castleman Disease Symptoms and Diagnosis

The presentation of Castleman disease symptoms and diagnosis varies significantly depending on the type of disease. Unicentric Castleman Disease often presents as a painless, enlarged lymph node that may be discovered during a routine physical exam or imaging for another condition. Patients might experience mild, localized symptoms if the enlarged lymph node presses on surrounding structures.

In contrast, Multicentric Castleman Disease typically involves systemic symptoms due to widespread inflammation and cytokine overproduction. These symptoms can be debilitating and include:

• Persistent fever and night sweats
• Unexplained weight loss
• Profound fatigue and weakness
• Enlarged lymph nodes in multiple areas (neck, armpits, groin)
• Enlarged liver and spleen (hepatosplenomegaly)
• Fluid retention (edema)
• Nerve damage (neuropathy)
• Anemia and other blood count abnormalities

Diagnosing Castleman Disease requires a comprehensive approach. A definitive diagnosis relies on a lymph node biopsy, where a tissue sample is examined under a microscope for characteristic cellular changes. Imaging studies, such as CT scans or PET scans, help identify enlarged lymph nodes and assess the extent of the disease. Blood tests are also crucial to check for inflammation markers, anemia, abnormal protein levels, and to rule out other conditions. For MCD, testing for HHV-8 and HIV is essential to guide treatment strategies.

Castleman Disease Treatment Options

The selection of Castleman disease treatment options is highly dependent on the type of disease and its severity. For Unicentric Castleman Disease (UCD), surgical removal of the affected lymph node is often curative. If complete surgical excision is not feasible due to the location or size of the mass, radiation therapy may be considered as an alternative or adjuvant treatment to shrink the lymph node and alleviate symptoms.

Treatment for Multicentric Castleman Disease (MCD) is more complex and typically involves systemic therapies aimed at controlling inflammation and reducing the overgrowth of immune cells. These treatments may include:

• Immunosuppressants: Corticosteroids like prednisone are often used to reduce inflammation.
• Monoclonal Antibodies: Drugs such as siltuximab, which targets interleukin-6 (IL-6), a cytokine implicated in MCD, are a primary treatment for idiopathic MCD. Rituximab, which targets B-cells, is often used for HHV-8-associated MCD.
• Chemotherapy: In severe or refractory cases, or when associated with lymphoma, chemotherapy regimens may be employed to suppress immune cell proliferation.
• Antiviral Therapy: For HHV-8-associated MCD, antiviral medications may be used in conjunction with other treatments.

The goal of MCD treatment is to manage symptoms, prevent organ damage, and improve the patient’s quality of life. Treatment plans are highly individualized, often requiring collaboration among hematologists, oncologists, and other specialists. Ongoing monitoring is essential to assess treatment response and manage potential side effects.