Brachial Plexus Neuritis Associated With Anti–Programmed Cell Death-1 Antibodies: Report of 2 Cases

Recently, guidelines have been outlined for management of immune-related adverse events occurring with immune checkpoint inhibitors in cancer, irrespective of affected organ systems. Increasingly, these complications have been recognized as including diverse neuromuscular presentations, such as demyelinating and axonal length–dependent peripheral neuropathies, vasculitic neuropathy, myasthenia gravis, and myopathy. We present 2 cases of brachial plexopathy developing on anti–programmed cell death-1 checkpoint inhibitor therapies (pembrolizumab, nivolumab). Both cases had stereotypic lower-trunk brachial plexus–predominant onsets, and other clinical features distinguishing them from Parsonage-Turner syndrome (ie, idiopathic plexitis). Each case responded to withholding of anti–programmed cell death-1 therapy, along with initiation of high-dose methylprednisiolone therapy. However, both patients worsened when being weaned from corticosteroids. Discussed are the complexities in the decision to add a second-line immunosuppressant drug, such as infliximab, when dealing with neuritis attacks, for which improvement may be prolonged, given the inherent slow recovery seen with axonal injury. Integrated care with oncology and neurology is emphasized as best practice for affected patients.