Castleman disease (giant lymph node hyperplasia) is a rare disorder of the lymph nodes and lymphatic tissues -- the main parts of the immune system. The condition causes an abnormal overgrowth of cells that increases the size of affected lymph nodes. It also affects how the body produces white and red blood cells, lymphocytes, platelets, and other immune system cells. Castleman disease is not cancer, but as the symptoms are extremely similar, diagnosis can be difficult.
Symptoms of Castleman disease vary, and some people experience none at all. In some cases, the individual will develop lumps under the skin at lymph node sites. These lumps can interfere with breathing if they are in the chest because they put pressure on the windpipe and other respiratory organs. Lumps in the abdomen can cause a feeling of fullness that could lead to unintentional weight loss or trouble eating. Other symptoms of Castleman disease include fever, serious infection, nausea, leg swelling, and skin rashes.
Castleman disease can be mistaken for lymphoma, rheumatoid arthritis, and other common diseases, so ruling them out is the first step of diagnosis. The doctor will examine the lymph nodes in the neck, under the arms, and in the groin to note their size. He will also order blood tests to identify low levels of red blood cells and high levels of antibodies, which will present if the patient has Castleman disease. Pictures of the chest and abdomen can show the size of the lymph nodes there. Finally, the doctor will biopsy suspect lymph nodes.
After confirming Castleman disease, the doctor must determine how much of the body the disease has affected. The disease is unicentric (UCD) if it affects lymph nodes in just one area. This type is most common in the chest and abdomen. It is multicentric (MCD) if it affects multiple lymph node areas, including organs with lymphatic tissue. This latter form is more difficult to treat.
If a person has multicentric Castleman disease (MCD), the doctor must next determine the presence of human herpesvirus-8 (HHV-8). HHV-8 attacks the immune system, leaving the body too weak to fight off HIV or other autoimmune diseases. Interestingly, though, not everyone with HHV-8-associated MCD has HIV. In these cases, the condition is termed idiopathic MCD or iMCD.
Looking at the affected tissue under a microscope is the final step. This helps further identify the type of Castleman disease present as well as appropriate treatment. If the cells are hyaline vascular, the disease is probably unicentric with few symptoms. This is the most common type. Plasma cells point to multicentric with symptoms. The tissue may also contain both hyaline vascular and plasma types; this suggests multicentric with symptoms.
No one knows what causes UCD, though research links it to an autoimmune disorder. The cause of iMCD is also unknown. Researchers speculate that an acquired or inherited genetic mutation causes the condition. However, there is currently no evidence to support that. HHV-8-associated MCD is the only type of Castleman disease for which the cause is known.
If the affected area is small enough, a surgeon can remove it completely. This is the most common and most successful treatment for UCD. If the area is too large to remove surgically, medication can shrink the area enough for surgical removal. Even removing most of the affected area can successfully eradicate the condition. When surgery is not an option, doctors often recommend radiation.
Antiviral drugs can combat the HHV-8 virus. They are also effective against HIV, if it is present. The doctor may also prescribe immunotherapy drugs, or chemotherapy and radiation. Some patients receive stem cell replacement therapy. However, that treatment is complicated and expensive and is usually not recommended.
Doctors may prescribe medication affects the amount of interleukin-6 the body produces. Interleukin-6 is a protein that helps regulate immune responses. The patient may also take anti-inflammatory medications or undergo chemotherapy. Unfortunately, about half of the people who receive this treatment eventually quit responding. The doctor will often then begin hormone, targeted, or biological therapies.
The prognosis for UCD is good. Surgery removes the affected area and there is no relapse in most cases. Unfortunately, the statistics are not as good for MCD, partly because it affects more than one area and compromises the immune system, rendering the body less capable of fighting off infection. Luckily, research is making advances in antibody research and medications that target the immune system.
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