A patient with Castleman's disease initially manifesting symmetrical synovitis with pitting oedema

Castleman's disease (CD), especially multicentric CD (MCD) has been known to manifest a variety of clinical features such as fatigue, anaemia, fever, and hypergammaglobulinaemia. Here, we report a 72-year-old female patient who had complicated severe synovitis, as an initial manifestation of the disease, lastly diagnosed as MCD. Initially, she had been diagnosed as remitting seronegative symmetrical synovitis with pitting oedema (RS3PE) syndrome because of bilateral leg pitting oedema with significant C-reactive protein and matrix metalloproteinase-3 elevation but no disease-specific autoantibodies. Promptly, corticosteroid and additionally weekly methotrexate were introduced, but her leg oedema and inflammatory findings did not adequately come to be a remission. A lymph node biopsy from the groin region was performed because multiple lymph node swelling in ultrasound examination appeared even after introducing treatments, which revealed mixed-type CD. Multiple lymphadenopathies were observed in the axilla and inguinal region; finally, we diagnosed her as idiopathic MCD and introduced tocilizumab, which significantly improved leg oedema as well as inflammatory findings. As is shown in this case, manifestations included in RS3PE syndrome could be one of the clinical phenotypes in MCD, which should be considered as a differential diagnosis of MCD.