Abstract Background Unicentric Castleman disease (UCD), a rare lymphoproliferative disorder, is frequently complicated by paraneoplastic pemphigus (PNP), an autoimmune mucocutaneous syndrome with high mortality. The hyaline-vascular (HV) histological subtype predominates in UCD-PNP, yet the mechanisms driving vascular hyalinization and stromal dysregulation remain poorly defined. Objectives To elucidate the cellular and molecular pathogenesis of UCD-PNP through integrated transcriptomic and cellular analyses, focusing on stromal-immune crosstalk and mechanisms underlying extracellular matrix (ECM) dysregulation. Methods We performed bulk RNA sequencing (RNA-seq) of lymph node (LN) samples from 33 patients with pathologically confirmed UCD-PNP and single-cell RNA-seq (scRNA-seq) in 5 of them. Analytical approaches included differential expression, pathway enrichment, cellular deconvolution, developmental trajectory inference, ligand-receptor interaction analysis, and spatial validation. Functional consequences of identified interactions were assessed using bulk RNA-seq and proteomic analysis. Results Bulk RNA-seq highlighted extracellular matrix (ECM) dysregulation, with significant upregulation of collagen genes in UCD-PNP. scRNA-seq of 58,811 cells revealed expansion of endothelial cells (ECs), pericytes, and fibroblasts, alongside diminished follicular dendritic cells (FDCs). Cell-cell communication analysis identified ECs as primary contributors to collagen/laminin overproduction via COL4A1-ITGA1/ITGB1 and LAMB1-ITGA6/ITGB1 signaling, directly linking EC activity to perivascular hyalinization. UCD-PNP also featured marked plasmablast expansion, IgG class-switching, and memory CD4+ T cells driving B-cell hyperactivity. In addition, ligand-receptor analysis revealed a pivotal interaction between EC-derived COL4A1 and CD44 on B cells. Mechanistically, COL4A1 overexpression in ECs upregulated genes involved in ECM organization and remodeling. Furthermore, proteomics revealed that endothelial-B cell crosstalk drived vascular basement membrane accumulation (Perlecan/HSPG2) and pro-inflammatory cytokine release (CCL4) in functional co-cultures. Conclusions UCD-PNP pathogenesis centers on aberrant EC expansion and dysregulation, driving simultaneous vascular hyalinization via excessive ECM deposition. Pathological endothelial-B cell interactions, directly link basement membrane accumulation to pro-inflammatory signaling. Targeting this EC-driven stromal-immune crosstalk presents a novel therapeutic strategy for UCD-PNP.
Wang et al. (Sat,) studied this question.