Cutaneous Plasmacytosis and Idiopathic Multicentric Castleman Disease: A Spectrum of Disease?

Cutaneous/systemic plasmacytosis (C/SP) is a plasma cell disorder characterized by reddish-brown patches, lymphadenopathy, and hypergammaglobulinemia. The degree to which C/SP overlaps with other plasma cell proliferative disorders and neoplasms is incompletely understood. We present the case of a patient with a several-year history of cutaneous plasmacytosis and evidence of systemic involvement with concurrent idiopathic multicentric Castleman disease (iMCD) involving a lymph node. There have been only a few reports of systemic iMCD preceded by a long, asymptomatic phase of cutaneous manifestations. We discuss the relationship between C/SP and iMCD and elaborate on the pathophysiological overlap of these 2 conditions and potential similarities in their pathogenesis. We suggest that the 2 diseases may represent the same entity presenting on a spectrum, with individuals diagnosed with C/SP at risk for progression to iMCD.