One autopsied case of chronic progressive sensory-ataxic neuropathy with polyclonal elevation of serum and CSF IgG and IgA and without malignancy is reported. A marked loss of large myelinated fibers was universal in both the central and peripheral rami of primary sensory neurons. Fiber loss showed a multifocal patchy pattern in the proximal nerve trunks. The posterior root ganglion cell bodies were moderately atrophic and loss of large cells was observed. Unmyelinated axons were well preserved. The ventral spinal roots, ventral spinal horn cells, and muscles showed minimal involvement. There were focal perivascular mononuclear inflammatory cells without necrotizing vasculitis around the endoneurial and epineurial vessels. Similar perivascular cellular invasions were observed in the visceral organs, occasionally forming germinal follicle centers. This case suggested that this neuropathy has a unique background with a possible immune-mediated basis.