Background: Increased intracranial pressure with encephalopathy has rarely been reported in Addison's disease. Method: Case Study. Results: A 16-year-old female who presented with cerebral edema of unknown etiology was eventually diagnosed as having Addison's disease. She had early morning headaches, fatiguability, diarrhea and deterioration in school performance. She was hyponatremie with a serum sodium of 128 mmol/L and hyperkalemic with a serum potassium of 5.9 mmol/L. She had a low serum osmolality (264 mosm), high urine osmolality (533 mosm) and high urine sodium (87 mosm). She had a postural drop in blood pressure and diffuse hyperpigmentation. An ACTH stimulation test revealed a low baseline Cortisol and no response to ACTH. Plasma renin activity was increased. Serum ACTH was elevated. She responded well to intravenous fluids and solu-cortef and was discharged on hydrocortisone and florinef. She remains well 18 months after the acute episode with no neurologic complaints or findings. Conclusion: Addison's Disease should be considered in the differential diagnosis of symptomatic cerebral edema and idiopathic intracranial hypertension.

although spontaneous recovery is possible, disability may accumulate over time. In the absence of MRI evidence of demyelination, it is a diagnosis of exclusion and patients need to be worked up for other pathologies. CONFLICT OF INTEREST None.