Rare Association Between Idiopathic Multicentric Castleman Disease, Nephrotic Syndrome and Polyneuropathy in an Immunocompetent Patient.

Multicentric Castleman disease (MCD) represents a group of poorly understood lymphoproliferative disorders related to proinflammatory hypercytokinaemia. In immunocompetent patients the aetiology is still unknown, hence the designation of idiopathic MCD (iMCD). To successfully diagnose iMCD, diagnostic criteria must be fulfilled and a large array of alternative diagnoses excluded. Peripheral neuropathy and nephropathy are relatively common findings in cases associated with POEMS syndrome, but very rarely reported in iMCD. We present the case of a 64-year-old man with iMCD (HIV- and HHV-8-negative) with nephrotic syndrome and severe motor polyneuropathy. Alternative diagnoses were excluded. The patient was treated with intravenous glucocorticoid followed by rituximab. Complete clinical and laboratory remission was achieved and maintained at the 2-year follow-up. LEARNING POINTS: iMCD is a lymphoproliferative disease in immunocompetent patients with no known cause.To diagnose iMCD major and minor criteria must be fulfilled, and alternative diagnoses must be excluded.Nephrotic syndrome and motor polyneuropathy are rare in iMCD and all alternative diagnoses must be excluded before relating all of these. © EFIM 2021.