Hypertensive crises are frequent in the emergency room. The term covers a group of syndromes that have in common high blood pressure. When accompanied by acute organ damage, it is known as a hypertensive emergency, as opposed to a hypertensive urgency, in which there is no such damage. One specific type of emergency is malignant hypertension, in which there are exudates and/or retinal hemorrhages or papilledema. Besides effective and prompt treatment, it is mandatory to screen for secondary causes of the hypertension. We present the case of a 40-year-old patient, with no previous history of hypertension, who was admitted for malignant hypertension. In this article we review the pathophysiology, clinical aspects and prognosis of this condition.