METHODS A 22-year-old female without relevant underlying medical conditions presented with an acute onset of dysphasia. Her blood pressure was found to be 190/90 mm Hg. METHODS Physical examination revealed left-sided hemiplegia and Broca's aphasia. A blood count showed anemia and thrombocytopenia. Cranial CT and MR imaging revealed small hypodense periventricular and cerebellar lesions. Mitral valve insufficiency and bilateral pleural effusion were found in echocardiography and chest x-ray, respectively. METHODS A hypertensive emergency with cerebral and cardiac end-organ lesions was diagnosed. Blood pressure could not be controlled despite combination therapy of intravenous antihypertensive drugs. A full check-up for secondary hypertension revealed systemic lupus erythematosus (SLE) and catastrophic antiphospholipid syndrome (APS). Treatment of SLE/APS resulted in considerable improvement of blood pressure. CONCLUSIONS After ruling out frequent causes of hypertensive emergencies, such as insufficient adherence to drug therapy of primary hypertension, or secondary hypertension caused by renoparenchymal disease or renal artery stenosis, vasculitis or systemic diseases like SLE should be considered.