Immune checkpoint inhibitors (ICIs)-related ocular myositis.

We present extensive clinical, serological, morphological and muscle imaging data of a 66-year-old man with isolated bilateral ptosis and external ophthalmoplegia secondary to Immune checkpoint inhibitors (Pembrolizumab). He had elevated CK level (>5000 UI/L). No facial, bulbar, proximal, distal or axial muscular weakness was observed. Electromyography (EMG) showed myopathic pattern, with spontaneous activity. Myositis specific antibodies and anti-striational antibodies were negative. Cardiac and respiratory functions were preserved. Skeletal muscle MRI was unremarkable, whereas extraocular muscles revealed bilateral hyperintensities in inferior rectus, medial rectus and superior oblique muscles in both T1 and STIR sequences, with mild muscle atrophy. Muscle biopsy showed endomysial inflammatory infiltrates, MHC-1 expression was observed in clusters of non-necrotic cells. CD56 positive cells were observed in perifascicular regions. Patient discontinued Pembrolizumab and received corticosteroid treatment with progressive clinical improvement and CK normalization. Our findings support this clinical entity, suggesting that isolated ocular myositis represents a subgroup of generalised myositis with predominant ocular symptoms.