BACKGROUND Catatonia can be divided into non-malignant or malignant. The latter is characterized by autonomic instability, exhibiting high fever, tachycardia and hypertension, and is regarded as a fulminant and rapidly progressive subtype. METHODS This article reports a case of malignant catatonia in a 43-year-old patient who had been presenting psychiatric disorders for the last three years. The patient was stable, maintaining mutism, immobility and autonomic abnormalities. Oral lorazepam (1 mg every eight hours) was introduced and, in a few hours, the patient became afebrile. Two days later, the patient was already responding to verbal commands. CONCLUSIONS Early intervention with lorazepam reduced the evolution of this patient to a fatal complication. Therefore, this case report sought to show that early diagnosis and intervention reduced the occurrence of serious and irreversible clinical outcomes.