Small vessel platelet thrombosis in the peripheral nerves in POEMS syndrome.

Introduction/aims: Vascular thrombosis is prevalent among patients with polyneuropathy, organomegaly, endocrinopathy M-protein, and skin changes (POEMS) syndrome. The endothelial cells in the endoneurium are often hypertrophied and the lumen is frequently occluded. Consequent local hypoxia may increase vascular endothelial growth factor (VEGF), which induces hypercoagulation and vascular permeability.

Methods: This study presents two patients in the fifth decade of life, who had rare nerve biopsy findings of vascular occlusion mainly by platelets. Before the cases presented here, we encountered nine confirmed POEMS patients whose nerve biopsies did not show similar findings.

Results: A small artery and a vein were occluded, but no atherosclerotic changes were observed. The endothelial cells that adhered to the packed platelets lost their junctions.

Discussion: Platelet aggregation, degranulation, and ischemia may cause a loose endothelial barrier and leak proinflammatory cytokines, such as interleukin-12. This may increase production of VEGF and may cause nerve demyelination. Small vessel platelet thrombosis may contribute to the pathogenesis of this disorder.