Reversible encephalopathy syndromes are generally characterised by headache, confusion, seizures and visual loss. Malignant hypertension and immunosuppressive medications are often considered the main causes. We present a challenging case of reversible encephalopathy in a young man with epilepsy and autism in which malignant hypertension resulted in widespread cerebral white matter oedema with uncal herniation. Complete reversibility of the MRI findings with antihypertensives has been achieved over 6 months coupled with complete clinical improvement. At presentation this 19-year-old man was found unrousable and febrile. He required intubation and treated for seizures and a meningo-encephalitis. CT brain showed generalised cerebral oedema. On intensive care he improved, was extubated on day 9, became hypertensive on day 10, remained alert until day 13, then became unresponsive with a blood pressure of 230/110 mm/Hg. CT brain showed vasogenic oedema with bilateral uncal herniation and on MRI a diffuse leuko-encephalopathy. CT venography was normal. Sodium nitroprusside was required as blood pressure remained uncontrolled with propofol, midazolam, alfentanil, atracurium and labetalol. After one week control was achieved and maintained with ramipril, bisoprolol and amlodipine. Recovery was complicated by bowel obstruction requiring resection with histology confirming Crohn’s disease. Presently he is back to his baseline cognition and undergoing neurorehabilitation.