Pembrolizumab-induced Myasthenia Gravis: Literature Review of Ocular Manifestations and a Refractory Case

Immune checkpoint inhibition is a new and promising therapy approved for the treatment of various malignancies. Pembrolizumab is a potent tumor suppressor that acts by upregulating the immune system to recognize cancer cells which may result in disrupted self-tolerance. We describe a case and perform a literature review of myasthenia gravis with ocular manifestations after treatment with pembrolizumab. Our case had bilateral ptosis refractory to conventional treatment, and she remained functionally blind as a result. The literature review included 28 cases of immune-related myasthenia gravis, and a 30% mortality rate excluding deaths from primary cancer progression was shown. Under half had full symptom resolution (n=13, 46%), and there was no clear correlation between specific management strategies and prognosis. Patients with isolated ocular myasthenia gravis (n=9, 32%) were twice as likely to be symptom-free after treatment compared with generalized myasthenia gravis (75% vs. 39%). Respiratory involvement was associated with twice the mortality rate (60% vs. 33%) and triple the risk of noncomplete symptom resolution (20% vs. 61%). The majority of cases had their pembrolizumab discontinued (n=20, 71%), but 3 were successfully rechallenged by utilizing prophylactic low-dose steroids. Patients with immune-related myasthenia gravis experience increased mortality and morbidity but if steroid-responsive, may benefit from the reintroduction of anti-programmed cell death protein 1 therapy for end-stage malignancy with close monitoring. A high index of clinical suspicion for immune-related adverse effects are critical in an era of rising immunotherapy use.