SUN-282 Transient Infundibulohypophysitis in a Child with Central Diabetes Insipidus

Case Description A 7-year-old previously healthy female presented with a 1-month history of tiredness, excessive thirst and increased urinary frequency. Initial studies showed an elevated serum osmolality with relatively dilute urine. She underwent a water deprivation study which confirmed central diabetes insipidus (CDI). An MRI of the brain was obtained which showed markedly thickened and homogeneously enhancing pituitary stalk thickening (17mm craniocaudal x10 mm anteroposterior diameter). Workup did not reveal any signs suggestive of Langerhan’s cell histiocytosis; a skin biopsy and bone survey were normal. A pituitary stalk biopsy was scheduled, however direct endoscopic visualization of the pituitary stalk was normal, so the procedure was aborted. A repeat MRI 7 weeks later showed complete resolution of the stalk thickening. An MRI done 4 months later again showed normal anterior pituitary and normal pituitary stalk, with persistent absent posterior bright spot. She remains on desmopressin, and anterior pituitary functions have been normal to date. Discussion CDI in children can be due to infectious, neoplastic, traumatic or genetic processes that disrupt the hypothalamus or pituitary stalk. One third of children with CDI present with pituitary stalk thickening (PST) on initial evaluation with MRI. There are wide variations in the degree of PST. Previous studies have shown that the degree of PST is different depending on the underlying etiology. Furthermore, regression of PST has been observed in many cases of CDI with PST which has been attributed to idiopathic or autoimmune process (infundibulohypophysitis). Most studies have demonstrated that PST > 4 mm is unlikely to regress and may be more likely to progress with eventual diagnosis of a neoplastic process such as germinoma or Langerhan’s cell histiocytosis. Based on review of the literature, the earliest resolution of PST was in 3 months in a patient who received steroid therapy at diagnosis. [1] Conclusion Our case illustrates that in children with central diabetes insipidus, isolated pituitary stalk thickening may resolve in as short a period as 7 weeks. While ongoing evaluation is warranted with serial pituitary imaging, unnecessary invasive procedures may be avoided in patients without evidence of other underlying anatomic pathology. Anterior pituitary function requires initial and continued surveillance. References 1. Shaefers J et al. Clinical presentation and outcome of children with central diabetes insipidus associated with a self-limited or transient pituitary stalk thickening, diagnosed as infundibuloneurohypophysitis. Clin Endocrinol (Oxf). 2017 Aug;87(2):171-176. doi: 10.1111/cen.13362. Epub 2017 Jun 5.