Clinical Reasoning: A 60-Year-Old Man With Asymmetric Weakness and Persistent Fever.

Peripheral neuropathies, especially those with atypical features, remain a diagnostic challenge. In this case, a 60-year-old patient presented with acute-onset weakness starting in the right hand then sequentially involving the left leg, left hand, and right leg over 5 days. The asymmetric weakness was accompanied by persistent fever and elevated inflammatory markers. Subsequent development of rashes combined with careful review of the history led us to the final diagnosis and targeted treatment. This case highlights clinical pattern recognition with the help of electrophysiologic studies in peripheral neuropathies, which provide shortcuts to narrow the differential diagnosis. We also illustrate the important pitfalls from history taking to ancillary testing in diagnosing the rare but treatable cause of peripheral neuropathy (eFigure 1, links.lww.com/WNL/C541).