Castleman disease.

Castleman disease (CD), a heterogeneous group of disorders that share morphological features, is divided into unicentric CD and multicentric CD (MCD) according to the clinical presentation and disease course. Unicentric CD involves a solitary enlarged lymph node and mild symptoms and excision surgery is often curative. MCD includes a form associated with Kaposi sarcoma herpesvirus (KSHV) (also known as human herpesvirus 8) and a KSHV-negative idiopathic form (iMCD). iMCD can present in association with severe syndromes such as TAFRO (thrombocytopenia, ascites, fever, reticulin fibrosis and organomegaly) or POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder and skin changes). KSHV-MCD often occurs in the setting of HIV infection or another cause of immune deficiency. The interplay between KSHV and HIV elevates the risk for the development of KSHV-induced disorders, including KSHV-MCD, KSHV-lymphoproliferation, KSHV inflammatory cytokine syndrome, primary effusion lymphoma and Kaposi sarcoma. A CD diagnosis requires a multidimensional approach, including clinical presentation and imaging, pathological features, and molecular virology. B cell-directed monoclonal antibody therapy is the standard of care in KSHV-MCD, and anti-IL-6 therapy is the recommended first-line therapy and only treatment of iMCD approved by the US FDA and EMA.