Acute respiratory failure is an uncommon initial presentation of myasthenia gravis (MG). In our case a 22-year-old woman of unrecognized MG presented to the emergency department with isolated respiratory failure as the first presenting symptom. Initially she presented with dysphonia and was managed by speech therapist and ENT surgeons for 3 months. Subsequently, she presented with signs and symptoms of sepsis and went into acute respiratory failure. This case highlights the need to consider MG in the differential diagnosis of an otherwise unexplained respiratory failure in the critical care setting.