Five biopsies, one diagnosis: challenges in idiopathic multicentric Castleman disease

A previously healthy 29-year-old man initially presented to the hospital with pleuritic chest pain and shortness of breath. Over the next 2 months he developed ongoing fevers and night sweats with recurrent exudative pleural effusions and ascites. He had an extensive infectious and autoimmune workup that was unremarkable. He had an initial lymph node biopsy that showed reactive changes only. He had an acute kidney injury and his renal biopsy revealed thrombotic microangiopathy. His liver biopsy showed non-specific inflammatory changes. His bone marrow biopsy showed megakaryocyte hyperplasia and fibrosis, which raised suspicion for the thrombocytopenia, ascites, reticulin fibrosis, renal dysfunction and organomegaly syndrome subtype of multicentric Castleman disease. This prompted a repeat lymph node biopsy, showing changes consistent with mixed type Castleman disease that fit with his clinical picture. He was initiated on steroids and siltuximab with significant clinical improvement.