Case Presentation: A 71-year-old woman with poorly differentiated squamous cell carcinoma (SCCA) of the left cheek with recent initiation of nivolumab therapy presented to the Emergency Department with five days of bilateral thigh pain, generalized weakness, and dyspnea. The exam was remarkable for tachycardia, hypotension, tachypnea as well as neck and proximal muscle strength weakness. [...]