Idiopathic Multicentric Castleman Disease Presenting With Generalized Lymphadenopathy: A Case Report

Idiopathic multicentric Castleman disease (iMCD) is a rare non-clonal lymphoproliferative disorder characterized by systemic immune dysregulation and generalized lymphadenopathy, often mimicking infectious, autoimmune, and neoplastic diseases.We present the case of a 66-year-old woman with hypothyroidism and significant unintentional weight loss who was admitted with progressive dyspnea, generalized weakness, hypotension, diffuse lymphadenopathy, bibasal crackles, and ascites.Initial evaluation revealed cytopenias, elevated inflammatory markers, acute kidney injury, electrolyte abnormalities, hypoalbuminemia, diffuse lymphadenopathy, bilateral pleural effusions, ascites, and anasarca.Persistent hypotension, renal dysfunction, refractory hyperkalemia, and low serum cortisol levels raised clinical suspicion of adrenal insufficiency.After multiple initially non-diagnostic lymph node biopsies, a subsequent cervical lymph node biopsy demonstrated histopathological and immunophenotypic findings consistent with iMCD of the mixed histological subtype, with negative human herpesvirus 8 testing and no histological evidence of malignancy.The diagnosis was established according to the Castleman Disease Collaborative Network criteria after evaluation for infectious, autoimmune, and neoplastic mimics.Intravenous hydrocortisone led to hemodynamic stabilization, renal recovery, correction of hyperkalemia, and improvement in platelet counts.The patient subsequently received rituximab, cyclophosphamide, and prednisone, with an initially favorable clinical response.However, her subsequent course was complicated by right femoral artery thrombosis requiring above-knee amputation and, later, shock associated with an extended-spectrum betalactamase-producing Escherichia coli infection, as well as progressive renal failure requiring hemodialysis.This case highlights the diagnostic complexity of iMCD and the importance of integrating clinical, laboratory, imaging, and histopathological findings, particularly when probable adrenal insufficiency is part of the initial presentation.