An unusual case of HHV-8 negative, idiopathic, multicentric Castleman disease following chronic lymphocytic leukaemia

Background: Castleman disease is a rare condition characterised by polytypic lymphocytes proliferation and lymphadenopathy generally with a benign course. Whereas high grade lymphoma (Richter syndrome) is a classical complication seen in chronic lymphocytic leukaemia with a poor outcome, benign conditions mimicking this entity are infrequent. Case description: We describe the case of an 81-year-old Caucasian male who developed a human herpesvirus-8 (HHV-8)–negative, idiopathic multicentric Castleman disease (iMCD) following a treated Binet C chronic lymphocytic leukaemia (CLL). The clinical and radiological pattern raised initially the suspicion of a classical Richter transformation. Blood analysis showed auto-immune haemolytic anaemia and thrombocytopenia. He had normal immunoglobulin levels. The anatomopathological analysis of a cervical adenomegaly showed hypervascularisation and a polytypic plasmocytic proliferation compatible with a plasmocytic iMCD type. Interestingly, bone marrow examination showed reticuline fibrosis but, in the absence of anasarca or generalised oedema, we were not allowed to conclude to the diagnosis of a TAFRO syndrome. We exclude all other mimicking conditions, comprising haematological malignancies, infections, and auto-immune diseases He was first treated with corticosteroids with poor results but dramatically responded to tocilizumab (anti-Il6). Conclusion: To our knowledge, this the first case described of a Castleman disease following CLL and surprisingly mimicking Richter syndrome. Clinicians should be aware of this rare misleading condition.