Introduction: Rasmussen’s encephalitis (RE) is an infrequent chronic neurological disorder characterized by unihemispheric inflammation of the brain cortex, refractory epilepsy, and progressive motor and cognitive decline. The presentation in adulthood is uncommon and represents around 10% of the cases. Case Report: A 54-year-old woman developed focal myoclonic seizures involving the right face and upper limb. The seizures were recurrent and progressed to Epilepsia partialis continua. Gradually, she developed cognitive impairment. The magnetic resonance imaging showed left unihemispheric frontoparietal moderate atrophy compared to the baseline magnetic resonance imaging. Rasmussen’s encephalitis was diagnosed according to the Bien criteria. The antiepileptic drug combination treatment partially controlled the seizures. After pulses of methylprednisolone, the patient was discharged seizure-free. Conclusion: Rasmussen’s encephalitis is rare in adults; however, it should be considered as a differential diagnosis in patients with a history of pharmacoresistant focal seizures with progressive involvement of higher functions and imaging studies showing cerebral hemiatrophy. Current pharmacological treatment for this condition does not include the use of steroids. Nevertheless, in this case, methylprednisolone represented a treatment option in a limited-resource context.