Myasthenic crises can occur spontaneously during myasthenia gravis natural history; they can also be triggered by several factors, such as concomitant infections, pregnancy or drugs. Interferon has been implicated in myasthenic crisis, as well as ribavirin. No data are available about new antiviral drugs for the treatment of hepatitis C virus (DAAs). Here we report the case of a 73-years old man affected by myasthenia gravis and HCV genotype 2a/2c chronic hepatitis, who developed a myasthenic crisis during sofosbuvir and ribavirin treatment. Even if myasthenia gravis is a rare disease, the correlation of myasthenic crises, either direct or indirect, with the use of the new DAAs has to be taken into consideration.