Drug-induced myasthenic syndromes

Drug-induced myasthenic syndromes are caused by numerous medications of various classes. D-penicillamine and interferon alpha lead to an autoimmune process similar to spontaneous myasthenia gravis, whereas many other agents produce weakness by a direct compromise of neuromuscular transmission. A particular problem in clinical practice is the deterioration of neuromuscular transmission by anesthetics and neuromuscular blocking drugs. Moreover, novel drugs may show myasthenia-like syndromes or exacerbation of preexisting myasthenia gravis during clinical studies or in post-marketing surveillance. In this article, the author draws attention to the rare occurrence of drug-induced myasthenia with a new class of anticancer drugs, the immune checkpoint inhibitors. These include the drug ipilimumab targeting cytotoxic lymphocyte-associated protein 4 (CTLA-4), and the drugs nivolumab and pembrolizumab targeting programmed cell death-1 (PD-1). Management of drug-induced myasthenia in these cases requires withdrawal of the immune checkpoint inhibitor and standard immunotherapy including high-dose steroids.