ESPE Abstracts

Introduction: Diabetes insipidus (DI) is a rare disease in children. In most cases it is acquired and central in origin (CDI). The most frequent cause of acquired CDI is brain tumor and idiopathic forms represent between 20-50% of cases, depending on the series. Autoimmune hypophysitis is a rare cause of DI and is a presumptive diagnosis with a suggestive brain MRI and ACTH and TSH deficiencies as the most common hormonal involvement, although it can manifest with diabetes insipidus in the case of predominant involvement of the pituitary stalk. Anti-pituitary autoantibodies are not sensitive nor specific. We present the case of a 6-year-old boy with an initial diagnosis of idiopathic DIC that was later diagnosed as possible autoimmune hypophysitis.

Clinical case: 6-year-old boy referred to the ER due to polyuria and polydipsia. During his admission a water restriction test is carried out and CDI is diagnosed. Desmopressin is started with a good response. Pituitary hormones and tumor markers are normal and brain MRI shows the absence of the typical bright spot of the neurohypophysis. The MRI control 4 months later reveals a thickening of the pituitary stalk with extension to the neurohypophysis without local compression of adjacent anatomical structures. The diagnosis of idiopathic DIC is ruled out and the patient is admitted at the referral centre to complete the study. Tumor markers in the CSF are negative and rule out dysgerminoma; the imaging study rules out osteolytic lesions or other stigmas of histiocytosis. Hormonal control shows TSH 3.5 mIU/L, FT4 0.59 ng/dl, Cortisol 6.4 mcg/dl and IGF-I 70 ng/ml (-0.6 SD). Adrenal insufficiency is ruled out with an ACTH stimulation test and treatment with levothyroxine is started. It is oriented as possible autoimmune hypophysitis and a conservative management is decided through clinical, analytical and radiological follow-up. 12 months after the onset of the clinical symptoms there has been a decrease in the growth velocity and treatment with GH is planned to be started soon given the stability of MRI images.

Conclusions: Idiopathic DI is rare in children and requires periodic follow-up to rule out underlying organic lesions. Autoimmune hypophysitis is a rare entity whose diagnosis must be accompanied by strict follow-up through ophthalmologic control, brain MRI, pituitary hormones and tumor markers. There are no conclusive studies regarding treatment in the pediatric age group, but conservative management is a good alternative if there are no compression symptoms.