THU213 Posterior Reversible Encephalopathy Syndrome As A Rare Presentation Of ACTH-dependent Cushing Syndrome In A Pediatric Patient

Disclosure: E.E. Bell-Sambataro: None. C. Tatsi: None. P. Chittiboina: None. S.A. Bowden: None. Background: Cushing disease (CD), caused by ACTH-secreting pituitary adenoma, is the most common cause of Cushing Syndrome (CS) in children > 5 years of age. Hypertension is reported in up to 50% of pediatric cases with CS. We report a challenging pediatric case with a rare presentation of hypertensive emergency associated with CD. Clinical Case: A 6-year-old female with 3 month-history of rapid weight gain (8 kg), round face, and hypertrichosis presented to emergency department for abdominal pain from nephrolithiasis and was noted to have severe hypertension. While in ED, she developed status epilepticus and altered mental status. Brain MRI findings were consistent with posterior reversible encephalopathy syndrome (PRES). Her hypertensive encephalopathy gradually improved with aggressive anti-hypertensive and anti-epileptic therapy. Further studies confirmed hypercortisolism with markedly elevated urine free cortisol of 1288 ug/day (<18 ug/day) and lack of diurnal variation of serum cortisol (8 AM cortisol of 47.9 ug/dL, midnight cortisol of 20.3 ug/dL). ACTH level of 23 pg/mL suggested ACTH-dependent CS. Low dose (1 mg) dexamethasone suppression test (DST) failed to suppress 8 am cortisol (31.4 ug/dL). High dose DST (120 mcg/kg) suppressed serum cortisol to 67%- borderline threshold for CD, likely due to increased dexamethasone clearance by anticonvulsant. Pituitary MRI did not reveal a visible lesion. Desmopressin stimulation test showed stimulation of ACTH by 700% and cortisol by 160% suggesting pituitary source. Inferior petrosal sinus sampling showed a mildly increased gradient in central to peripheral plasma ACTH of 1.7 at baseline (>2) and post-stimulation of 2.5 (>3). ACTH gradient did not reach cutoffs for pituitary source, likely due to insufficient catheterization of petrosal sinus from anatomically small blood vessels. Given her severity, she underwent surgical pituitary exploration. Postoperative morning cortisol was <5 mcg/dL, with decreased midnight salivary cortisol level obtained 2 months after surgery. She developed post-operative central hypothyroidism but did not have diabetes insipidus. She had a 4 kg weight loss with increased height percentile 5 months after surgery and remains under close monitoring. Conclusion: PRES is a clinical-radiographic disorder characterized by seizures, encephalopathy with neuroimaging findings of reversible cortical and subcortical vasogenic edema. Hypertension induced by marked hypercortisolism precipitated by pain is likely the etiologic factor. Prompt recognition and treatment of PRES are crucial to prevent further life-threatening complications and permanent neurological damage. Early diagnosis and treatment of CD are critical to prevent associated morbidities. Pituitary exploration by expert neurosurgery team should be considered in patients with MRI-negative CD. Presentation: Thursday, June 15, 2023