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.

Most melanocytic tumors can be characterized as a benign nevus or a melanoma by a trained pathologist using traditional histopathological methods. However, a minority demonstrates ambiguous features and continues to be a diagnostic challenge. Genetic expression profiling (GEP) assays have been developed in an effort to resolve this dilemma. These assays measure mRNA levels of specified genes using reverse transcription quantitative polymerase chain reaction technology. The development of GEP assays, methodology, challenges associated with GEP validation and testing, and the suitability of a currently available GEP test for clinical use are reviewed.

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Pointsc Skin IL-9, calprotectin, and KIR gene expression may be predictive of subsequent kidney involvement in patients with IgAV. c Histologically similar patients with IgAN, IgAV, and IgA-IRGN can be distinguished by their immune transcriptomes. c Kidney biopsies from patients with IgA-IRGN are enriched for transcripts involved in granulocyte chemotaxis.