Biomarkers and Signaling Pathways Implicated in the Pathogenesis of Idiopathic Multicentric Castleman Disease/Thrombocytopenia, Anasarca, Fever, Reticulin Fibrosis, Renal Insufficiency, and Organomegaly (TAFRO) Syndrome.

Idiopathic multicentric Castleman disease (iMCD) and TAFRO syndrome present a variety of symptoms thought to be caused by excessive inflammatory cytokines and chemokines, but the underlying mechanisms are unknown. iMCD is broadly classified into two types: iMCD-NOS and iMCD-TAFRO, which have distinct laboratory findings, pathological features, and responses to treatments. It is thought that iMCD-NOS, particularly the IPL type, responds favorably to IL-6 inhibitors due to its IL-6-centric profile. iMCD-TAFRO frequently progresses acutely and seriously, similar to TAFRO syndrome. Elevated levels of cytokines, including IL-1β, TNF-α, IL-10, and IL-23, as well as chemokines like CXCL13 and CXCL-10 (especially in iMCD-TAFRO), SAA, and VEGF, have been linked to the disease's pathology. Recent research has identified key signaling pathways including PI3K/Akt/mTOR and JAK-STAT3, as well as those regulated by type I IFN, as crucial in iMCD-TAFRO. These results suggest that dominant pathways may vary between subtypes. Further research into the peripheral blood and lymph nodes is required to determine the disease spectrum of iMCD-NOS/iMCD-TAFRO/TAFRO syndrome.