POEMS syndrome is a plasma cell dyscrasia that presents with numerous complications, one of which is rarely pulmonary hypertension. Here we present a case of POEMS syndrome with pulmonary hypertension who improved with steroids and six rounds of plasmapheresis done over 1 month, and we document the baseline immune mediator status and the changes associated with the therapeutic intervention. Serum levels of soluble immune mediators such as interleukin (IL)-5, IL-8, IL-10, and eotaxin were normal at baseline and throughout therapy, whereas those of tumor necrosis factor (TNF)-alpha, soluble TNF-receptor type I (sTNF-RI), IL-6, interferon (IFN)-gamma, IL-2, and sIL-2R, which were abnormally high at baseline normalized with steroids and plasmapheresis. Serum levels of sIL-6R, which were abnormally low at baseline, increased to normal after therapy. The latter results pinpoint not only potential mediators of the systemic manifestations of POEMS syndrome with pulmonary hypertension but also relevant markers in patient follow-up. In this respect, IL-6 has been involved in the pathogenesis of multiple myeloma and Castleman's disease, and the interplay between abnormally high levels of IL-6 and abnormally low levels of its soluble receptor, deficiencies that corrected with therapy in this patient, appears to be particularly relevant to the pathogenic manifestations of POEMS syndrome with pulmonary hypertension. These findings are discussed in the context of our current knowledge of the pathogenesis of pulmonary hypertension and of potential new therapeutic modalities for POEMS syndrome with pulmonary hypertension.