Serum Soluble Interleukin-2 Receptor as a Potential Marker for Assessing Disease Activity in the TAFRO Subtype of Idiopathic Multicentric Castleman Disease

Idiopathic multicentric Castleman disease (iMCD) accompanied by thrombocytopenia, anasarca, fever, reticulin myelofibrosis/renal insufficiency, and organomegaly (TAFRO) frequently develops into prolonged severe thrombocytopenia and multiorgan dysfunction, which is associated with a high mortality rate. We herein describe three cases of iMCD-TAFRO in which serum soluble interleukin-2 receptor (sIL-2R) levels varied in relation to disease activity following the initiation of treatment. Thrombocytopenia persisted for several weeks to months after the normalization of the patients' C-reactive protein levels, whereas their sIL-2R levels normalized 10-47 days prior to platelet recovery (≥100×10⁹/L). The serum sIL-2R measurement may therefore be an effective method for evaluating the disease activity in iMCD-TAFRO patients with prolonged thrombocytopenia.