To report a case of hereditary transthyretin (TTR) amyloid neuropathy unmasked by bortezomib chemotherapy for multiple myeloma.

Multiple myeloma is associated with peripheral neuropathy in many ways, including paraprotein effects, amyloid deposition and treatment-induced toxicity. In rare cases, an underlying neuropathy of alternative etiology may be unmasked by chemotherapy treatment, posing diagnostic challenges.

Case report.

A 59-year-old woman was diagnosed with kappa free light chain multiple myeloma after presenting with acute renal failure. Prior to the diagnosis, she had mild numbness in the toes for years but never sought medical attention. She developed acute onset numbness, tingling and pain soon after starting treatment with bortezomib, cyclophosphamide and dexamethasone.  Neuropathy symptoms continued to worsen despite the cessation of the chemotherapy. On physical exam, she had distal more than proximal weakness in both arms and legs, as well as loss of vibration sensation in the toes. Electrodiagnostic testing revealed moderate to severe subacute sensorimotor polyneuropathy. The prominent motor involvement was atypical for bortezomib-related sensory neuropathy. Vascular endothelial growth factor (VEGF) was normal and there were no other features of POEMS syndrome. Given the moderate velocity slowing, bortezomib-induced inflammatory demyelinating neuropathy was considered. Lumbar puncture showed normal opening pressure, normal cell count and protein of 99 mg/dL. A trial of intravenous immunoglobulin (IVIG) was given, but she had no clinical improvement. Given the left ventricular wall thickening on echocardiogram, genetic testing for hereditary TTR amyloidosis was pursued, which revealed V122I mutation in the TTR gene. She was started on patisiran.

We demonstrate a case of hereditary TTR amyloid neuropathy unmasked by bortezomib chemotherapy. While neuropathy is common in multiple myeloma with chemotherapy, a careful clinical investigation is warranted to look for alternative etiologies in atypical cases.