Introduction: Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure without an evident cause. Obesity and the female sex have been recognized as risk... Show moreIntroduction: Idiopathic intracranial hypertension (IIH) is characterized by increased intracranial pressure without an evident cause. Obesity and the female sex have been recognized as risk factors for the development of this syndrome. Until now, Graves' disease has only been described in the literature as the probable cause of IIH in 7 patients. This report describes the case of a young girl with Graves' disease presenting with symptoms of intracranial hypertension (IH). Case Presentation: A 21-month-old girl presented with progressive symptoms of poor weight gain and bilateral exophthalmos. She also experienced difficulty sleeping, diarrhea multiple times per day, irritability, and heat intolerance. Laboratory investigation showed elevated free T4, fully suppressed TSH, and elevated anti-TSH antibodies, consistent with a diagnosis of new-onset Graves' disease. She was successfully treated with monotherapy thiamazole, titrated to the lowest possible dose of 1.25 mg once daily with normalization of thyroid function tests within 3 months of treatment initiation. After 18 months of treatment, her condition unexpectedly deteriorated as papilledema and slight esotropia were found at a routine checkup. An MRI and lumbar puncture showed increased intracranial pressure, but no underlying anatomical cause for the IH was found. Acetazolamide therapy was started, and papilledema in both eyes resolved within weeks. Unfortunately, papilledema has recurred several times over the following 2 years when attempts were made to decrease the acetazolamide dose. Discussion/Conclusion: This case report is the first to describe a very young patient who developed significant IIH in the chronic stage of Graves' disease. IIH development seemed to be related to the progression of the Graves' ophthalmopathy, rather than initiation of thiamazole therapy or fluctuations in serum fT4 levels. Show less