The largest retrospective cohort was reported from the Mayo Clinic by Dupont et al. Nineteen of their 208 patients with POEMS syndrome experienced ischemic stroke, and a subgroup analysis of 90 patients among whom nine had a stroke revealed no difference in the vascular endothelial growth factor or IL-6 levels or traditional stroke risk factors (such as age, diabetes, hypertension, smoking, and cardiac arrhythmia) between the stroke and nonstroke groups. This evidence concerns the gene IL6 and chronic obstructive pulmonary disease.