Bortezomib is a proteasome inhibitor demonstrating substantial activity in multiple myeloma. One of its key toxicities is peripheral neuropathy, which is reversible in most patients. The possibility that bortezomib might in rare cases induce severe neuropathies by auto-inflammatory mechanisms remains controversial. We report here the case of a 65-year-old female myeloma patient who was initially treated with bortezomib, doxorubicin, and dexamethasone (PAD). At the end of the second cycle of PAD, the patient presented with a rapid and severe onset of paresis of the left arm, accompanied by progressive sensory neuropathy and increasing neuropathic pain. After an extensive neurological work-up, including electrophysiological and laboratory evaluations as well as magnet resonance tomography imaging, we diagnosed an inflammatory autoimmune neuropathy, presumably induced by bortezomib, with accentuation of the left arm nerve plexus. We subsequently initiated regular treatment with polyvalent immunoglobulins, which gradually improved the neurological symptoms. In conclusion, the identification of an inflammatory autoimmune neuropathy, presumably associated with bortezomib, is a rare but important complication. An extensive neurological examination should be performed in patients who develop severe or unusual sensory or motor deficits under therapy with bortezomib, so as to differentiate autoimmune from toxic neuropathies, as therapeutic strategies differ for each.