Disclosures: Diana M. Molinares: Nothing to disclose

Case Description: We highlight two cases of skeletal weakness (de novo myasthenia gravis and myositis) that were related to recent immunotherapy treatment.

Setting: Inpatient tertiary cancer hospital.

Patient: 65-year old male with metastatic clear cell carcinoma on a clinical trial with sitravatinib and nivolumab, who presented with shortness of breath, neck pain and weakness, and ptosis. Fatigability test was positive for ptosis and diplopia on sustained up-gaze and proximal bilateral upper extremity weakness. The patient had elevated CK and EMG revealed findings of post neuromuscular junction dysfunction, likely myasthenia. He received solumedrol, pyridostigmine, mestinon and IVIG for 5 days, along with physical and occupational therapy with significant functional gains. However, he developed a large right pelvic hematoma and respiratory failure requiring ventilatory support. His acetylcholine receptor antibodies (AChR-Abs) and myositis-antibodies were positive. His respiratory status continued to deteriorate and underwent a palliative extubation that resulted in his death.

Assessment/Results: Case-2: 83-year old male with metastatic urothelial carcinoma on clinical trial with pegylated IL-2 and nivolumab. After his second cycle, the patient reported neck weakness, hoarseness and difficulty swallowing. Left rectus femoris biopsy showed focal inflammatory cells and EMG suggested myopathy with irritable features (fibrillations and positive sharp waves). He was diagnosed with myositis. The patient received treatment with solumedrol, PLEX, physical and occupational therapy. He had functional improvements, however developed respiratory failure and requiring intubation. Workup showed positive AChR-Abs and he was diagnosed with myasthenia crisis. He received a course of IVIG with significant improvement and continued to make functional gains.

Discussion: Clinicians treating cancer patients should respond quickly if presented with new onset skeletal muscle weakness after immunotherapy. Rehabilitation professionals have an important role in the recovery of patients with immunotherapy-related muscle skeletal weakness.

Conclusion: With new treatment modalities emerging in the field of immunotherapy, clinicians must be aware of the development of immunotherapy-related side-effects.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/immunotherapy-related-skeletal-muscle-weakness-in-cancer-rehab-patients-a-case-series/