Dichotomic response to interleukin-6 blockade in idiopathic multicentric Castleman disease: two case reports.

Background: Human herpervirus-8/human immunodeficiency virus negative Idiopathic multicentric Castleman disease (iMCD) is a lymphoproliferative disorder sustained by a pro-inflammatory condition of hypercytokinemia mostly mediated by Interleukin-6 (IL-6). According to iMCD consensus guidelines, anti-IL-6 blockade should be the first-line therapy for iMCD. However, despite the existing therapeutic alternatives, a large proportion of iMCD patients still lacks an effective therapy.

Case Presentation: Here, we report two real-life iMCD cases with a different response to IL-6 blockade. The first presented patient obtained a prompt resolution of symptoms and a complete regression of adenopathies after IL-6 blockade therapy administration. Conversely, the second patient did not respond neither to Rituximab and Etoposide association nor to IL-6 blockade therapy (both Siltuximab and Tocilizumab). Furthermore, Intravenous immunoglobulin, Cyclosporine A, Sirolimus and anti-Interleukin-1 Anakinra were all attempted without any results. Since no treatment was successful, after a further confirmation of iMCD diagnosis by a second lymph node biopsy, patient has been candidate for thalidomide, cyclophosphamide and prednisone association therapy.

Conclusions: The iMCD cases we reported are coherent with the evidences that IL-6 blockade is a safe and an effective therapy for iMCD. Despite this, more than half of patients do not respond to anti IL-6 drugs. In such cases, therapeutic alternatives could be represented by Sirolimus, targeting PI3K/AKT/mTOR signaling or by associations of conventional drugs such as thalidomide, cyclophosphamide and prednisone. However, the two reported iMCD cases, confirm the need to more deeply investigate iMCD pathogenesis and to better dissect the heterogeneity of the disease in order to develop novel, effective therapeutic strategies.