ESPE Abstracts

A 5-years-old boy was admitted because of polydipsia and polyuria. His family history was unremarkable. After water deprivation test (10h), laboratory test showed high levels of serum sodium (150.1 mmol/L), low urine osmolarity (88 mOsm/kg) and high serum osmolarity (301 mOsm/kg) consistent with the diagnosis of central diabetes insipidus (CDI). He started therapy with oral desmopressin with clinical improvement. Brain MRI revealed pituitary stalk thickening (3 mm), no hyperintense signal in the neurohypophysis. CBC and inflammatory markers were negative. No other pituitary defects. In order to highlight the underlying aetiology of CDI, a close follow-up was started and the patient underwent subsequent clinical-instrumental evaluations and further examinations. Autoimmune and infectious diseases were excluded. Tumour markers (AFP, beta-HCG) on serum and CSF were negative. Imaging (chest and total body X-ray, abdominal ultrasound) was normal. No pituitary biopsy was performed because of the risks of the procedure and the absence of urgent indications. Two years after the presentation, the patient reported a skin nodule on the left cheek. During a complete physical examination, sparse nodules were observed in multiple locations. Two lesions were biopsied and the histology showed dermal proliferation of histiocytic cells. Immunoperoxidase studies showed the cells to be CD1a, S-100 and CD207/langerin negative, CD68, CD163, CD14 positive, suggestive for non-Langerhans histiocytosis (non-LHC). Immunohistochemistry also detected the presence of BRAF V600E point mutation. These findings oriented the diagnosis within a clinicopathologic spectrum including extracutaneous juvenile xanthogranuloma and Erdheim-Chester disease. Due to the diagnostic difficulty, after multidisciplinary evaluation, the lesion has been currently defined as non-X histiocytosis, no further classified. No mutation of BRAF was found in peripheral blood and CSF. The patient follow-up is currently ongoing with regular check-ups: MRI shows reduction of the pituitary stalk thickening. To date, the tumour markers are negative, the instrumental examinations are normal. The diagnosis of isolated CDI raises the question of its aetiology: patients must undergo complete clinical examinations, routine surveillance for new lesions, periodic blood tests and brain MRI. Non-LCH is a rare entity in paediatric age, with predominantly cutaneous manifestations; however few cases of non-LCH are reported with internal organ involvement, including CNS and CDI. In this case, the clinical course, the radiological and histopathological features, could suggest a form of non-LCH with CNS involvement, but it’s an hypothesis to be confirmed. For avoiding pituitary biopsy, further evaluation and follow-up is needed to determine a definitive diagnosis.