A 66-year-old man developed paresthesia of the distal parts of the bilateral lower limbs a week after his upper respiratory infection, followed by the weakness with the legs and paresthesia with the lip area, tongue and finger tips. Those symptoms gradually became worse to the point that he was unable to walk 10 days later. Although skin pigmentation, edema, and lymph node swelling were not found, we made a diagnosis of Crow-Fukase syndrome (CFS) because of clinical features of polyneuropathy, IgG-lambda type M proteinemia, endocrinological abnormality, elevated plasma level of vascular endothelial growth factor (VEGF) and extramedullary plasmacytoma in his abdomen. Following intravenous immunoglobulin therapy (IVIg), he showed marked improvement. However, his neurologic symptoms deteriorated acutely just after open biopsy together with the elevation of VEGF level, and a few days later he was in the state of flaccid quadriparesis. We tried IVIg therapy again and his neurologic symptoms were markedly improved. We speculated that an elevated VEGF, released from plasma cells induced by the bioprocedure, might have caused an increase in microvascular permeability and affected the blood-nerve-barrier, thereby his neurologic symptoms deteriorated. It is thought that this case may support the hypothesis that a significant role is played by VEGF in the pathomechanism of the development of CFS. Additionally we experienced that IVIg was very effective to the neurologic symptoms, and we think that IVIg will be able to be one of the future therapy of the CFS. To our knowledge, there has been no report of CFS which manifested acute deterioration of his neurologic symptoms just after open biopsy with acute onset with Guillain-Barré syndrome like symptoms.