Pembrolizumab-induced necrotizing diaphragmatic myositis

Abstract

Pembrolizumab, an anti-PD1 antibody, is increasingly used for the treatment of non-small cell lung cancer. We report a severe and poorly described adverse effect of this therapy: necrotizing myopathy with diaphragmatic and myocardial involvement. A 77-year-old male was diagnosed with metastatic lung adenocarcinoma and started a regimen with chemotherapy along with Pembrolizumab. Two weeks after the second cycle, he was admitted to the hospital due to acute myocarditis and hypercapnic respiratory failure. Treatment with glucocorticoids and Mycophenolate improved his cardiac condition. However, hypercapnic respiratory failure persisted, as well as orthopnea and generalized muscle weakness including bulbar musculature. After comprehensive evaluation including diaphragmatic ultrasound, electromyogram, and biopsy, he was diagnosed with autoimmune necrotizing myopathy with diaphragmatic and myocardial involvement. Treatment with intravenous immunoglobulins and non-invasive mechanical ventilation was added. However, he experienced respiratory deterioration, resulting in death. This case exemplifies the importance of early recognition and intensive treatment of this serious adverse effect. Due to the increasing use of these therapies, it is expected to see a parallel increase in their adverse effects in the coming years. Keywords: Pembrolizumab, necrotizing diaphragmatic myositis