(Kiosk 1) Functional Recovery Following Immunotherapy-induced Myasthenia Gravis: A Case Report

Case Diagnosis: An 82 year old male with history of Non-Small Cell Lung Cancer (NSCLC) developed myasthenia gravis (MG) as an adverse effect related to Pembrolizumab treatment.

Case Description or Program Description: One week after receiving his 4th cycle of Pembrolizumab for treatment of NSCLC, the patient developed difficulty swallowing, extremity weakness, right eyelid drooping, and difficulty taking full breaths which progressively worsened over several weeks. This eventually led to hospitalization for respiratory distress, evaluation by neurology and a subsequent diagnosis of immunotherapy-induced MG. Given his functional impairments of severe dysphagia, decreased endurance, decreased balance, and generalized weakness, he was admitted for acute inpatient rehabilitation.

Setting: Inpatient Rehabilitation Facility

Assessment/Results: Despite having debilitating immunotherapy-induced MG, he was able to participate fully in a rehabilitation program consisting of 3-4 hours per day of speech & language pathology, physical therapy, and occupational therapy. Therapists focused on strength and endurance of respiratory muscles, energy conservation techniques and extremity range of motion with prevention of contractures. Although this case differed from the typical presentation and course of the more common autoimmune MG, the rehabilitation plan was similar and effective: goal-oriented therapies to improve functional independence and decrease caregiver burden upon return home.

Discussion (relevance): Immune checkpoint inhibitors are a common treatment selection for patients with oncologic disease, and growing numbers of patients formerly treated with PD-1 inhibitors such as Pembrolizumab and Nivolumab are being admitted to acute inpatient cancer rehabilitation centers. Although these therapies have improved outcomes for patients with malignancies such as NSCLC, renal cell carcinoma, and melanoma, there is also growing evidence of immune-related adverse effects. MG is one of the uncommon but known neuromuscular junction disorders that can be triggered by PD-1 inhibitor use. Given its rarity, this condition can be a diagnostic challenge, and there is a lack of existing evidence regarding functional outcomes for patients that acquire immunotherapy-induced MG.

Conclusions: Patients with immunotherapy-induced MG have potential to make significant functional gains and may be appropriate to consider for acute inpatient rehabilitation admission. As indications for immune checkpoint inhibitors expand, it is important for physiatrists to recognize and be able to manage side effects of this therapy.