Autoimmune myasthenia gravis is rarely seen during infancy. Similar to adults, 85% to 90% of generalized pediatric myasthenia gravis cases have acetylcholine receptor antibodies. Approximately 30% of the remaining cases have antibodies against muscle-specific kinase. Information on the clinical course, treatment alternatives, and prognosis of pediatric muscle-specific kinase antibody–positive myasthenia gravis is limited because of the small number of cases. Here, we present a 14-month-old girl with muscle-specific kinase antibody–positive myasthenia gravis as one of the youngest patients described so far in the literature.