Multicentric Castleman Disease (MCD) is a rare disease that affects the lymph nodes and related tissues. It is a form of Castleman disease that is "systemic" and involves multiple regions of lymph nodes (as opposed to unicentric Castleman disease, which involves a single lymph node or single region of lymph nodes). The signs and symptoms of MCD are often nonspecific, and are mild in some people but serious in others. Symptoms may include enlarged lymph nodes in multiple regions, fever, weight loss, nausea, rash, and/or an enlarged large liver and spleen. The disease is diagnosed based on the symptoms present, laboratory test results, imaging studies, and results of a biopsy of the lymph nodes which shows specific features when studied under the microscope. In some cases, MCD is caused by human herpesvirus-8 (HHV-8) and is referred to as HHV-8-associated MCD. In other cases, the cause is not known and it is referred to as HHV-8 negative MCD, or idiopathic MCD (iMCD).