Castleman disease (CD) describes a group of rare lymphoproliferative disorders that involve enlarged lymph nodes, and a broad range of inflammatory symptoms and laboratory abnormalities.

These are differentiated by the number and location of affected lymph nodes and the presence of human herpesvirus 8, a known causative agent in a portion of cases.

All forms involve overproduction of cytokines and other inflammatory proteins by the body's immune system as well as characteristic abnormal lymph node features that can be observed under the microscope.

[4] Doctors classify the disease into different categories based on the number of enlarged lymph node regions and the underlying cause.

[citation needed] The exact cause of UCD is unknown,[2] but appears to be due to a genetic change that occurs in the lymph node tissue, most similar to a benign tumor.

Some UCD patients, however, experience systemic inflammatory symptoms such as fever, fatigue, night sweats, weight loss, and skin rash as well as laboratory abnormalities such as elevated C-reactive protein.

[6][7] In this form, patients have multiple regions of enlarged lymph nodes with characteristic microscopic features, flu-like symptoms, and organ dysfunction due to excessive cytokines or inflammatory proteins.

[9] HHV-8-associated MCD patients have multiple regions of enlarged lymph nodes and episodic inflammatory symptoms due to uncontrolled infection with HHV-8.

First-line treatment of HHV-8-associated MCD is rituximab, a drug used to eliminate a type of immune cell called the B lymphocyte.

[12] Castleman disease is defined by a range of characteristic features seen on microscopic analysis (histology) of tissue from enlarged lymph nodes.

Staining with latency-associated nuclear antigen (LANA-1), a marker for HHV-8 infection, should be measured in all forms of Castleman disease but is positive only in HHV-8-associated MCD.

[18] Formal diagnostic criteria and definition of the disease was established in 2016, which will allow for better understanding and the ability to appropriately track and research CD.