Case of idiopathic multicentric Castleman's disease: the master mimicker

A woman in her 20s with no medical history presented with progressive abdominal distension, right-sided abdominal discomfort, fatigue and nausea. Examination showed multifocal lymphadenopathy and hepatomegaly with tense ascites. Investigations revealed a multisystem inflammatory condition characterised by elevated acute phase reactants, anaemia, thrombocytopenia, acute kidney injury, lymphocytic ascites, hypoalbuminaemia and hypergammaglobulinaemia. HIV and human herpes virus-8 tests were both negative. In the presence of elevated ANA and SS-A/Ro antibodies, the patient was suspected to be carrying a connective tissue disease, most likely systemic lupus erythematosus (SLE). Clinical and laboratory findings fulfilled the diagnostic criteria for SLE. However, lymph node biopsy showed interfollicular plasmacytosis, associated with high interleukin 6 (IL-6) and vascular endothelial growth factor titers, together hinting towards a rare diagnosis of multicentric Castleman's disease (MCD). As we investigated further, renal biopsy was consistent with thrombotic microangiopathy which has been previously reported in MCD. Furthermore, immune staining on the renal biopsy was negative for 'full-house' immunoglobulin and complement staining pattern, which is specific for lupus nephritis, helping us exclude SLE. In light of these new findings, the patient was started on anti-IL-6 therapy which provided a successful outcome.