A Case Report of Drug-Induced Myopathy Involving Extraocular Muscles after Combination Therapy with Tremelimumab and Durvalumab for Non-Small Cell Lung Cancer

Recently developed anti-tumour therapies targeting immune checkpoints include tremelimumab and durvalumab. These agents have incompletely characterised side effect profiles. The authors report a 68-year-old man treated for non-small cell lung cancer (NSCLC) with a combination of tremelimumab and durvalumab. After treatment he developed diplopia, ptosis, fatigue, weakness, and an inflammatory myopathy affecting the extraocular muscles requiring hospitalisation. Electromyography (EMG) testing and muscle biopsy suggested inflammatory myopathy without sign of myasthenia. Within 1 month of withdrawal of cancer therapies and initiation of oral steroid therapy, ocular and systemic symptoms had resolved. This notable adverse effect has not been previously described for these drugs administered singly or in combination, and ophthalmologists should be aware of this presentation in patients treated with these agents.