Abstract Details

Case 1.

A 68-year-old woman presented with subacute asymmetric dysesthesias, numbness, and weakness of both arms and evidence on EMG of a sensory and motor axonal mononeuropathy multiplex of the upper extremities. She was found to have an IgM kappa monoclonal gammopathy and treated unsuccessfully for atypical neuropathy associated with Waldenstrom’s macroglobulinemia, despite an uninformative left radial sensory nerve biopsy. Her neuropathy progressed over weeks. She then developed paralysis of the right hemidiaphragm and restrictive lung disease, subsequently succumbing to respiratory failure. On autopsy, she demonstrated amyloid deposition in both hemidiaphragms and lung vasculature and parenchyma that was not subtyped but presumed to be AL amyloid given the monoclonal gammopathy.

Case 2.

A 62-year-old man presented in 2012 with progressive weakness of the wrist and finger extensors, evolving over a year and half. EMG studies demonstrated evidence of a pure motor axonal mononeuropathy multiplex of the upper extremities. He was given a presumptive diagnosis of multifocal motor neuropathy and was treated sequentially with intravenous immunoglobulin, rituximab, and cyclophosphamide with no improvement and continued slow decline. He then underwent a fascicular biopsy of the left radial nerve and brachioradialis muscle which showed amyloid deposition, subtyped by mass spectrometry as AL kappa.

This report highlights the importance of considering amyloidosis in the differential diagnosis of mononeuropathy multiplex, to prevent significant delays in identifying the disease and in initiating appropriate treatment. As was true also of two previously documented cases, these subjects presented with symptoms in the upper extremities, suggesting that this pattern may be more common when amyloid infiltrates peripheral nerve focally.