Single cell transcriptomic data of 12 samples collected from twins with Multicentric Castleman Disease and an unaffected sibling

Idiopathic Multicentric Castleman Disease (iMCD) is a rare IL-6-driven hematological disorder characterized by systemic lymphadenopathy, elevated immunoglobulin levels, and prominent plasmacytosis in the bone marrow and lymph nodes. Here, we present an unusual occurrence of iMCD in identical twins. Using single cell sequencing, we identified nodal endothelial cells and fibroblastic reticular cells as the source of IL-6 signals. An “inflammatory” peripheral monocytosis enriched for the expression of S100A family genes was evident in both twins, as well as a group of monocytes expressing cytotoxic gene signatures in the affected twin with milder clinical manifestations. Single-cell RNA-seq (scRNAseq) libraries were prepared from tissue samples from Twin-CS (lymph node and bone marrow), as well as from peripheral blood mononuclear cells (PBMC) from the affected twins and unaffected sister. Tissues were dissociated into single cells using the Tumour Dissociation Kit, human (Miltenyi Biotec, Bergisch Gladbach, Germany) as per manufacturer’s protocol. To better examine the lymph nodal cells from Twin-CS, two additional independent libraries were generated and combined for downstream analysis.